What are the effects of completely filling tires with water instead of air?

I happened to do just that.

I took an old hand pump and an inner tube to the bath tub.  Submerged the pump and pre-filled the tube with water, complete with burping out any air bubbles.  With the tube moderately full and free from air, I put it on the rim with the tire.  Then the final pressure up.

The first thing to notice is that the pump operates with lots of resistance (water flows a lot slower than air through those tiny parts).

As I pushed each stroke of the pump, the resistance difficult yet constant.  I kind of expected the resistance to increase as I pressured up the tire, but it didn't.  It was a solid stopping point, halfway through the last stroke the tire wouldn't take any more water. (I shouldn't have been surprised, water is one of the least compressible substances around!)

Now out for a ride to test this out!

Indeed to carry the bike the front was a bit heavier (heavier is exactly what most cyclists would not want; but hey, lets see if there's some benefits).

Oddly, the bike didn't feel all that different.  Just slightly front heavy.  But once I got some speed the steering became really quite stable.  A ride through the forest and I could quickly pin point my leans for corners, it was soooo smooth!  Like the steering of a motorbike; I assume the extra rotational inertia in the front wheel added to the smoothing gyroscopic effect.

Mucking about, I tried a wheelie.  It took a bit of getting used to for lifting it up, but once up it was also very very smooth.  I was never that good an wheelies, but now I seemed to be able to ride for as long as I wanted.  Try balancing a baseball bat with the heavy side down, it's actually much easier with more weight at the top!  And the extra gyroscopic effect made it easier to steer the wheelie.

When stopped at a light or something, pick up the front tire and it would slowly start to rotate on it's own.

It was fun, so I kept it.

The next phenomenon was a puncture.  sure enough, one day riding on a nice sunny day... I feel tiny sprinkles of water; I had a tiny tiny leak and I was actually spraying a very fine stream.  The tire hadn't lost much though, so I double timed it to my destination in hopes of avoiding changing in the field.  On arrival, the tire seemed really quite full still.  When off the bike the tire really wasn't getting flat. I left it.  I continued to ride for a week or so, sometimes the leak would come back... sometimes it would go away.

I'm speculating, as I only did this once... but it occurred to me that with water being incompressible, the small amount of leaking water was very little volume but nearly all of the pressure.  The tire was still full and held it's shape, but no pressure to force the leak when I wasn't on it (it was obviously a very small leak).

Eventually I had to add some air, now and again (too lazy to put water in, and too curious to see how bad the water/air mix would be).  Soon the water/air mix was sloshing inside and causing a lot of resistance, and that became the end of my experiment.

In the end I did not see any improvement for hill climbs, or maintaining pedal momentum; only wheelies and cornering.


I'm reading the question as saying there's too little pad gap and it's causing rub as well as lever travel that seems too tight/short/firm.

The first thing to do with any problem of this nature is to try pushing the pistons back in (after cleaning the outside if needed) and re-adjusting the caliper centering. Pistons that have somehow gotten pushed out too far can cause all the problems you're having. Some good tools to do this are a tire lever or an 8mm box wrench against the piston faces directly, or a degreased cone wrench, table knife, etc against the pads. It can help to slightly lubricate the pistons first with whatever fluid the system uses (DOT 3/4 fluid in this case) after cleaning them, in case drag when passing through the caliper seals is causing retraction issues.

Overfill per se is not usually the problem, although it is possible to overfill a brake using an incorrect bleed block. What usually gets mistaken for overfill is DOT fluid expanding due to absorbing water that makes it past the seals, because it absorbs water out of the air very readily. Most or all DOT fluid brakes seem like they do this to some extent over time, or at least can. (Mineral oil doesn't do this, which is one of its advantages). It's extremely common, for example, that a new bike that's been sitting warehoused halfway through a model year has this symptom when unboxed for assembly. When Juicy 3s were one of the most commonly specced brakes it seemed like half of them had this out of the box.

If you observe that the pistons can't be pushed back in fully on a DOT fluid brake, fluid expansion due to water contamination is the first thing to suspect.

The simple option is to "burp" a little fluid out by removing and putting aside the pads, putting a rag up to the caliper bleed port, slightly opening the port, and resetting the pistons with the port open (again cleaning/lubricating the pistons first as needed). Some fluid will come out, which the rag is there to soak up before it makes a mess. Close the bleed port quickly when you're done of course. This usually works fine for all intents and purposes. You are reducing the boiling point of the brake fluid every time you do this as well as increasing its compressibility, both of which could hypothetically make some kind of meaningful difference at some point, but we're really talking about a very small amount of water. You also shouldn't try this if you're not prepared to bleed the brake in case something goes wrong. I'll add the disclaimer that I haven't actually done this on Clark's brakes, only on many, many Avid/SRAM brakes. Wear gloves and eye protection.

You could also replace all the fluid, which is the safer and technically correct path if water contamination is suspected.


Why does a Bella cargo bike not act like a car driving in reverse?

You are not wrong to ask how tricky these things are to steer. They are very disconcerting to manoeuvre until you are quite familiar with them.

They certainly would be unstable at 30+ km/h. But good luck with that; you'd need to be quite an athlete to achieve such speeds. If you could pedal fast enough though, I think you would have a quite hilariously dangerous vehicle in your hands.

In practice, they are ridden at much lower speeds, where the rider doesn't find themselves caught out in ever-greater cycles of steering over-correction, and where the outward movement of the back end isn't rapid enough to be destabilising.


Are modern clipless shoes and pedals that much better than toe clips and straps?

Clipless pedals hold your feet more securely and release easier than toe-straps and clips. As you are probably aware, it is possible to to tighten straps to the point where they must be released before the foot can be removed from the pedal. A properly functioning clipless pedal will always release the riders foot.


Going on a long distance bike tour: what kit do I need?

For cycling across China you want a reliable bike that is unlikely to give you trouble, and which can be repaired with "local" resources if it does.

Forget about "lighter" wheels -- you want reliable wheels, and a pound less weight (if that) from a lighter wheel will not make any difference.  And I'd stay away from a geared hub, unless you can find one that you know is popular in China.

You do need a comfortable bar, but that's a personal thing and quite relative.

You should take at least two spare tubes, maybe a spare tire (see Sheldon Brown for how to fold it), patch kit(s), boots, and a good frame pump (don't rely on a "compact" model, and remember that you may have 20 flats, so going with CO2 alone is risky).  You should have some extra chain links and a chain tool (and make a crib sheet on how to use it), and maybe 2-4 "master links" of your favorite brand.  A few carefully chosen tools -- wrenches to fit seat bolt, crank arms, wheel axles (if not QR), etc.  And several spare spokes -- you generally need 3 sizes -- at least 2 of each.  Also, it's good to have the minimum tools needed to remove the cluster, in case you need to replace a spoke on that side.  (Assume that you can borrow, eg, a pipe wrench or some such to operate a cluster wrench.)  And don't forget the spoke wrench -- get a good quality one, not the one-size-fits-all ring thing.

Sun lotion, bug lotion, at least some "emergency" food, and a "road rash" first aid kit.  (Cortisone cream for bug bites is also often very handy, though toothpaste will work in a pinch.)

And whatever camping gear and clothing you need, based on how you will be traveling.  And, of course, maps, money (stashed several different places), lock for the bike (with extra cables to secure panniers), etc.

You might want to bring along some sort of trinkets to give to the locals as you meet them.  Simply some shiny new quarters would likely do, or you may have some other idea.


WIDER TYRES ARE FASTER

Every study on rolling resistance (including ones carried out by the leading tyre manufacturers) demonstrates clearly that wider tyres have LOWER rolling resistance and not just at the same pressure. This is also verified by many people (including myself) who use 25mm-28mm and much wider tyres on a regular basis and will never go back to anything narrower.

For vast majority of road cyclists there isn't a single rational reason (other than time trailing) for using 23mm tyres if the same model is available in 25 or 28 or wider width. On some bad roads (e.g. UK) it's actually unwise and dangerous to bounce around on such narrow piece of rubber.

There are several reasons why the myth of "fast" narrow tyres is still alive and kicking.

23mm is everywhere from the adverts, your local bike shop, cycling club to the TdF.
It's inconceivable for most of people to think that so many people around them could get it so wrong. Most of folks just go with the flow and don't ask questions.
People believe that they can "feel" rolling resistance and if narrow tyres are pumped up to its usual 100-120PSI it feels fast. You can't feel rolling resistance but you have to methodologically measure it with a power meter of some sort. Firmness and discomfort doesn't translate to speed, quite the opposite.
It's a common belief that rolling resistance is just a function of
a contact patch and the lower the contact area the faster the tyre is. The facts are that the shape of a contact patch and volume are more important than the total area.
People assume that rolling resistance is just about hysteresis (friction/resistance with the tyre itself) and nothing else. They are unaware of (or ignore) "suspension losses"
which occur on some less than perfectly smooth roads (most) and are about energy lost on lifting the rider/bike on imperfections of the surface.
For the same reason but on a much larger scale most of experienced mountain bikers with half brain run their tyres at a low pressure to go faster as even small obstacles (even bumpy field or gravel) are absorbed more effectively with less energy lost.
People confuse assumptions and beliefs with hard evidence. How many times you've read/heard: "Surely there is a reason why 23mm tyres are so popular..." "Surely if the pros use 23mm tyres..." Assumptions don't prove anything.
Some people (like one of the posters) have tried wider tyres and they found them slower.
Only comparing identical tyres in different sizes make sense and it's pretty obvious that a 23mm Michelin Pro3 is going to be faster than a 28mm Gatorskin due to a different design. Also the difference in speed that 2-3mm difference offers is most likely very small and can be only measured during repeated tests with a power meter at various pressure levels to find each tyre's sweet spot.
Many people have never tried anything wider as their frames/forks don't have enough clearance and more sensible and practical bikes taking wider tyres aren't "good/fast" enough for them or don't look right. They've never tried any fast wider tyres like Rivendell Jack Browns 33.3333mm or Schwalbe Kojaks 35mm or some fast 650B tyres. They have never run a pair of custom shaven completely bold 26x2.00 Schwalbe Furious Fred 120TPI 3oog mountain bike tyres on the road. It could be an eye opener.
Narrow tyres can be pumped up to higher pressures and higher pressure equals more speed. That's incorrect. As you increase the pressure, rolling resistance is going down but then at a certain point starts climbing sharply due to reduced ability of the tyre to conform to the non-perfect road surface (suspension losses). Even on a track/velodrome you won't benefit from 200PSI.
For every tyre width/volume, road surface and the rider's weight combination there is always an optimal (fastest) pressure. High pressure on its own means absolutely nothing.
The pros use it!
This the favourite argument of the defenders of status quo. You can't argue with it, can you?

Well... the pros ride at completely different speeds and therefore the aero benefits are probably more significant than rolling resistance. An average amateur rider would be naive to worry about the air flow differences between 23-28mm tyres.
Weight is also crucial as winning the stage / future career can be decided on a single climb. Again people worrying about the weight difference of several grams (rotating or not) may be slightly over-anxious.

The pros used to use 19mm tyres too in the past and now they are very slowly migrating to 25mm tyres. Were they wrong at the time, or are they wrong now or they will be wrong in the future? What if they discover that 28mm is even better? Will everyone be blindly following them?
The truth is that they are as guilty as you and me of being humans and use stuff that feels right and also aren't immune to peer pressure.

Road cycling community tends to be very traditional, conservative and protective of the status quo as I've experienced on other forums and in real life but for being open-minded and embracing "new" things can greatly benefit one's cycling.


Take a look at the specs for the rim (or tell us what kind of rim you've got). There are two ways to join a rim. One is to weld the joint, the other is to use a sleeve inside of the rim extrusion that aligns the ends.

If your rim is welded, then I would be inclined to agree with Carel. But it if is sleeved then it seems likely that what you're seeing is a slight imperfection in the alignment of the ends

There is no need to "adhere" the ends of the rim to each other. The load created by the spokes put the rim in compression. There is no tendency on a built wheel for the ends of the rim to pull apart. The point of welding or sleeving the joint is to keep the ends in alignment.


What is the optimum location / offset of a derailleur hanger vs axle?

Note on the rear of the Goatlink, there is a lump which should sit on the original rotation stop.

Shimano includes these diagrams in their rear derailleur documentation:

(source: peterverdone.com)


Hard fork and low tire pressure or viceversa?

I don't think tire pressure should be set on how cushy you want your ride (unless you have no shocks).

Tire pressure pressure and tread selection should be done based on how much traction you need. The trade off is that with more traction, you get a higher rolling resistance and you need to exert more energy to cover the same ground. This is why road bike tires look different than mountain bike tires.

More traction => Lower tire pressure, knobbier tiers.
Less traction => Higher tire pressure, smoother tires.

After you figure out what tread and tire pressure is best for you and your riding enviorment, then you can think about dialing in your fork and stiffness and damping.

Fork stiffness is somewhat subjective, but it's probably best to set it so that you only bottom out the shock when you take a pretty big hit. Most people set the stiffness of the fork based on sag, sag is the percentage that your shock deflects under your static body weight. Most people set their shocks to sag between 25-33%.

The fork damping (what you call rebound) should be set so that for your weight the fork is critically damped. No if's and's or but's about this one, physics dictates that the best ride is one where you are neither under or over damped.


Does dropping off a 4" kerb damage wheels?

Riding off a curb is not necessarily going to damage the wheel or tire. I do this pretty frequently on my road bike with narrow 23mm tires with no issues.

However, if you are a heavy rider, have cheap wheels, have under inflated tires  or use poor technique you could run into problems. If you can feel the rim hitting the ground then definitely don't do it.

Good technique is to approach reasonably slowly, stand up on the pedals and bend knees and elbows, shift you weight back onto the rear wheel as the front wheel goes over, the shift weight forward onto the front wheel as the rear wheel goes over. you can probably find some instructional YouTube videos easily.

If you have been doing this for a while and there are no obvious problems with your wheels, chances are they are fine. Check that the rims are true by spinning the wheel and watching the passage of the rim near a fixed point near the rim - brake pads for instance. Check the spoke tension by pinching pairs of spokes. If the rim is untrue or you have loose spokes get a local bike shop to true them up.


Difference between high and low pressure air springs?

To add to Daniel's comment, there is no real benefit/detriment to one vs the other, but you are going to find that rear shocks are typically higher pressure for a few reasons:

rear shock pistons are typically smaller in diameter and therefore require more pounds per square inch (PSI) to push back against load.
front shocks (ie your fork) are acting directly against the weight you're loading them with. For example, if when loaded the front wheel is supporting 50lbs, then the fork just needs to push back against 50lbs (minus the weight of the stanchions, front wheel, and front brake if you want to get technical about it). With many rear suspension designs, the linkage that hooks the shock ip to the rear triangle acts like a fulcrum, with the shock being on the short end of pivot, and thus it's not a 1:1 ratio of weight that the rear wheel is supporting vs the pressure with which the rear shock has to push back.
finally, weight distribution across a bike of the type in question is not 50/50 front and rear. The rear tire must support more weight when not under heavy braking. Therefore the rear shock is supporting more weight and must push back harder.


Do shops that sell used bikes normally also sell used parts?

They likely have "extra" bike parts around that are scavenged from bikes that were unrepariable, just be sure you know what your getting. There likely isn't any warranty included on used equipment, so if it was a "distressed" part that finally breaks a week after you've been using it, you be replacing it again. If you trust the bike shop and it is a reputable store that's been around for awhile, you should be fine. Nothing wrong with used parts, just so it fits and works correctly for its intended design, and doesn't appear to have been abused or been on a bike that was not maintained or has been wrecked.


How to mount central (two-legged) kickstand on normal bike frame

The groves are for any cables that are routed under the stays.
Your kickstand should have come with a counter plate - B in the picture below
Your kickstand is slightly different but the mounting instructions will be the same as the kickstand below
ergotec Double-leg kickstand Double Flex 3 manual

Bicycles without a stand plate

Check if the distance between the housing of the bottom bracket bearings
on the frame and the tyre of the rear wheel is sufficient for the assembly
operation.
Now you attach supporting surface C from below to the chain stay on the
frame. If there are cables here you press these into the notches D provided
for this purpose.
Adjust the double-leg kickstand in such a way that when folded into place
there is space of at least 15 mm between the kickstand and the tyre of the
rear wheel.
Now you place counter plate B on the chain stay from above and fasten it with clamping screw A.
Tighten clamping screw A to a tightening value of 21- 23 Nm.
Finally you check that the chain can move freely. For this purpose you should
engage all the gears once.


Are flat handlebars stable at high speed?

First off, understand that the geometry of the bike affects stability, especially the "marriage" between head angle and fork rake.  Adjusting these parameters (which can really only be "adjusted" by the frame builder) has a very dramatic effect on stability.

Beyond that, the hand position has an effect in a couple of ways.  First, if the hand position is more forward, it tends to "pull" the steering tube straight, reducing "responsiveness" and making it easier to hold the front wheel straight, while a more rearward position will make the steering more responsive and maybe "twitchy".  Similarly, an outboard hand position will allow the arms to brace the bar more, while an inboard position allows less torque to be applied to the steering tube.  Finally, when riding on the drops one can (with a bar of a certain geometry) brace the lower arm against the corner of the top of the bar, adding more rigidity than would be present with just the hands on the drops.

(Note that weight distribution (eg, how forward/aft and high/low the rider's center of gravity is) also has an effect.  Riding on the drops or not affects this to a degree.)

But remember that rigidity does not equal control.  A "stable" bike will take a bump and re-balance itself more or less automatically, due to steering tube geometry, et al, somewhat independent of hand position.  It's good to have a bar that allows you to apply the "desired" amount of torque to the steering tube (based on your preference for responsiveness vs stability), but if all that's doing is letting you fight poor inherent bike stability that's not a good trade-off.


Which tube size to prefer if several options apply?

Basically, the tube box will list the sizes it covers. Make sure your size is within those parameters (and ideally not "on the edge"). Beyond that you'd generally pick the lighter tube for road and the heavier one for off-road.  And a heavier tube will generally provide a slight improvement in puncture resistance.

Avoid very light tubes unless you're a racer, as they will often "leak down" much faster than heavier tubes, requiring you to inflate your tires twice daily in some cases.  (It would be nice if manufacturers rated their tubes based on leakage.)


Rider weight limits regarding a bicycle purchase

I bought a Mongoose Dolomite as an experiment.
Bottom line - It's poorly made, assembled, and designed.
Here is what I learned.

Four inch tires have no benefit of any kind in normal riding. (At least the tires on this bike anyway.  I didn't try in sand or snow so maybe there is some value somewhere.).
I was hoping to find a tire pressure that would be super comfortable - roll over cracks and bumps.
I experimented with tire pressures ranging from the recommended pressure to just 5 pounds in 5 pound increments. At the recommended pressure the tires were so bouncy the ride was very rough. At 5 pounds the pressure was so low the tire wanted to crawl off the rim and steering was dangerous. There was no happy place it was always too bumpy or too soft.
The bikes parts are poor quality.
From the wet noodle cranks arms to the stove pipe steel frame there was nothing close to adequate in component quality.
Nothing was assembled correctly.
To get this bike adjusted correctly everything has to be lubricated and adjusted. Every bearing group (always too tight), every cable, every nut and bolt has to be checked and adjusted.
The gearing was wrong.
The stock chain ring was too large causing the gearing to be a higher range (too hard to pedal) than worked well on the bike. I replace the wet noodle crank arms with a slightly better crank arms that had a triple chain ring and only used the smallest chain ring. This allowed the bike to be ride-able.(Sorry, I don't remember the tooth numbers. I made a video about my experience - should I link to it?).

Note: These are issues common to department store bikes.

If you enjoy attracting a lot of attention while riding your bike this is the bike to have. The fat tires drew a lot of attention.

Finding the right bike
mikes has a good suggestion - a used older steel frame mountain bike with no suspension.

Also, visit a local bike shop, more than one of them if possible. Be in "I'm only shopping" mode. Talk with them and see if they will let you test ride some bikes. This will help you form conclusions about what works for you.
There are many good bike shops that enjoy talking about bikes and helping people find the right bike for the task. If you find a shop that is high pressure or snobby just keep looking, good shops are out there.


Campagnolo has two cable pull numbers for 9 speed, theres 3.0 and 3.2 mm per click.

Shimano 9 speed is 2.5mm of cable pull per click, so you're out of luck.

I'd suggest selling on the campy shifters on ebay and use the proceeds to fund some boring but common shimano ones.

Or go the other way and look for a campag rear wheel and derailleurs, but these will likely be more rare and therefore cost more.

Reference link: http://blog.artscyclery.com/science-behind-the-magic/science-behind-the-magic-drivetrain-compatibility/


Do cyclocross races permanently damage the grass they are run on?

I've observed a number of cyclocross races in public parks in the area I live. These typically include paved areas, grassy areas and some dirt. If there's been rain recently (or raining during the race), the grass along the race course looks like it's been turned to mud. If you look more closely, you can see that the individual blades of grass are all intact, they're just bent over and muddy. A few months later, you can't even tell where the race course was anymore.

I believe it depends on the type of grass. For well-established and regularly mowed grass, such as is common in parks and for playing sports on, the damage is temporary and cosmetic. The ruts settle out on their own.

It seems like areas of slope that cause the racers to dig in and slip around more can get more damage.

Here's a photo essay of some cyclocross races the day of and several weeks later:
http://api.ning.com/files/zdPAeE6CK7J69K-gbRX4ru1-SAay5M6pkU6QqXD5QiNJnWx4-gdFn9oV0w47vypkoo67sVWzznYDLM4RwIDwgGVxfQP8Ivn0/AfterEffects.pdf (from http://www.ukcyclocross.com/profiles/blogs/after-effects-of-a-cyclocross).

Cyclocross races are generally run during a season that grass is dormant. It may not fully recover to looking nice until a few months later when the sunny/warm season starts up again.


What are the positions on drop bars called?

"Middle of the bar", "On the tops", "Middle", "Top", "Tops", "Center"

Hands on the part of the bar closest to the stem. The middle has some width and you can slide your hands around there.

"On the corners", "Corners"

Hands at the outside end of the section where the bar turns. You can grip the corner different ways. There's a sort of position in between corner and hood ("ramp"?), too.

"On the hoods", "Hoods"

Hands on the brake hoods. The brake hood is that rubbery thing that the brake lever comes out of and on a modern road bike likely also contains the shifter. There's different ways to put your hands on the hoods, I'm showing two I use.

"On the drops", "In the drops", "Drops"

In the lower curved part of the bar. With the drops you can be leaned way down with your hands far forward/up in the hoods, you can be about where I'm showing in the picture, or you can be on the lowest part of the bar (where you can't reach the brake lever).

Note for all of these:

There are various different hand positions in each of those main positions, but not necessarily names for them. Some of the differences can be subtle and don't really look much different, but change the pressure points on your hands.

Most road-bike riders primarily use the hoods, and that's generally what's currently encouraged. It's the most comfortable position that you can brake and shift from and gives you good leverage. The drops are your fastest position and also give you good leverage. Middle is most comfortable for your hands, but gives you the least control.


Having only my experience as source, it isn't a myth. Carbon forks tend to "copy" the road better, translating into a more soft riding experience for your arms. It makes the behaviour of the bike a little more "nervous" though.


My expectation with this design is that you'll be able to carry 15-25kg over a fairly rough track, if you built it reasonably well. Use the heaviest bike you can find as the donor, you want nice thick tubes. But it will probably fail by bending close to one of the joints. Bike tubing is not really designed to deal with bending.

With the design sketched I think that'll work fine with 26" wheels. The main thing will be welding the steering on the trailer frame/donor bike so it doesn't wiggle. Because the fork/wheel is going backwards the rake on the steering will be backwards, so if it's loose it'll be like trying to roll a castor backwards - very wiggly and unstable. Turning the fork round will help, but I suspect not much.

The suspension will probably not work as well as you hope because a fair bit of the force will be across the line of the suspension movement - rather than "brake dive" you'll have... nothing. I'd be tempted to try to get the fork more vertical, but that could end up making the design more complex and you're better off making something quickly, riding with it, then fixing the things that annoy you most once you have something that works.

Chainstays, your "bottom part", are really not designed to take bending loads, so that will be your weak point (assuming your welds hold). I would be tempted to brace those somehow, even just putting another tube between them with welded joints at the ends to reinforce that area will make the trailer stronger. If you have a space bit of tubing that would be well worth while. Gussets, BTW, will not help (here, or almost anywhere), they just shift the point of failure to the end of the gusset - designing an effective gusset is hard.

That ExtraWheel trailer design is all about a triangulated frame, and you could probably fake it using the seatstays and chainstays off two bikes, welded to a headset. It would probably be easier to build, but the attachment to your bike would probably be more tricky. I'd be tempted to bolt into the rack eyelets, if you have them, and see what happens.


Front hydrulic disc brake keeps going soft

As mentioned in comments you should get the brakes bled.

Doing it yourself is not hard, and there are many videos on YouTube showing how to do it. Park Tool has some very good how-to videos and articles. Here is the page for brake service.

Just make sure sure you get the correct kit and fluid for your specific brakes.


Dynamo light without rear light connected?

On old bikes usually the (steel) frame was used as second wire for closing the circuit. The old dynamo have one wire going out and some sort of built in electrical continuity with the frame.

First of all check that the bulb works, by using a trusted electricity source. Then:

If you bought a modern dynamo and a modern light, just lay an
additional wire between the two.
If you instead want to use a new dynamo with the old light, make sure
you connect one of the two outputs from the dynamo to the frame (a
washer in the right place will do the trick)

Not requested by your question: The rear light usually had connection to the frame via the mud shield (either it was made of metal, or had a metallic strip in the plastic body.


My tyre has hollow knobs, is it normal/desirable/essential for maker to disclose?

I don't think the tread blocks are 'hollow' exactly.

Tires are made up of layers of different formulas of rubber. I think you have worn though the outer layer and a little chip of rubber has flaked out of the center of some of the the blocks. Now you can see that the next layer down has de-laminated from the outer a little, so it looks like there is a void there.

If the blocks are hollow, the void is only right at the bottom of the block, and would only be exposed if the tire is very well worn, as yours is.


I think that their main point is not less weight but more control.  Imagine the normal 2-legged fork: even though the two sides are connected to the same air spring, you could concievably temporarily compress one more than the other, and now your front wheel is no longer pointed in the direction that the handlebars are.  This can only happen if the bridge is flexible, and typical fork bridges are very strong.

The Lefty avoids this by using a single stanchion, which can only move linearly, but now must be able to support twisting motion.  I do not know if Cannondale has succeeded in making it strong enough, but Leftys have been around for years, so it can't be too far off the mark.

And, note the many schemes for rear suspension.  There are many ways to suspend a bicycle; no single type is so good that all manufacturers must use it.  The same is apparently true for front suspension.


How much cable can I pull with a brake lever in another custom mechanism, and how can I achieve it?

I believe a typical V-brake lever (so called long pull) has enough action to pull 2 cm of a cable.

V-brakes are known for they greed for cable length - e.g. if replacing cantilevers with V-brakes one needs to replace the levers as well.

EDIT: I may be wrong - see this thread: What is the actual cable pull of brake levers?
There it says that long pull has the action of 14 mm which is not enough for you. A solution for you would be (depending on how technical/machinist savvy you are) to use the brake lever to engage another lever that increases the advantage of the cable pull.

Since one picture saves 1000 words...

This contraption would increase the pull of the secondary cable by the ratio of the arms of the extra lever at the cost of increased force required to engage the brake lever. Of course the extra lever can be in any shape and the distance between the rotation point and the cable attachment point determine the arm lengths.

I hope you get the idea.


What is this simulator like device called?

Rollers. You have three drums, two at the back, one at the front and the front roller is powered by one of the back rollers. You can also get add ons to give you a breeze:

Balance is what is needed to stay on the rollers, also a wall (as per featured video) comes in handy.

Rollers are used for training purposes although they can also be used for demonstrations at trade shows etc. When riding rollers instead of an exercise bike you do need to balance as well as push the pedals, you can therefore improve your riding, not just your strength/endurance.


Should I bike or drive to work? (6.8 mi)

I estimate 6.8mi as about 11km.  That is definitely doable for a novice, though it may not be as fast as Google's estimate at first.  Unless there aren't any traffic lights or stop signs, you should figure your overall average speed at no more than 15km/h initially, so budget 45-50min your first time out.  (Google is notorious around here for not allowing enough time for stop lights in their time estimates, and that's without having to get back up to speed.)

Of course once you've been doing it for a month you'll definitely start bringing that time down.

If you're asking in this forum, you have to expect we're always going to recommend that
you bike! :)  That said, there are places/roads that even I don't feel comfortable cycling regularly.  I can use them occasionally, but wouldn't want to ride them every morning and every night.  You'll want to check out the route so you know you'll feel safe (or have a bail-out option) even if it's a busy rush hour, or you get caught in a sudden rain, etc.

I would recommend taking a weekend morning and doing a test-ride to work, stop and have a coffee, then ride home.  Take at least a half hour break, unless you're feeling really good.  You can get a decent estimate of how long the ride will take.  Plus it's the weekend, so if you're slower on the return it's not a problem and it'll definitely give you confidence to do the ride on a regular workday.

Cycling to work is one of the best things about my current job; the exercise in the morning - especially on a sunny day - really helps me arrive at work in a good mood, energized and alert.  And the ride home literally helps burn off the stress of the day.


Food to keep in pannier long-term until it's needed?

I like to carry PowerBars, because they taste sufficiently foul that I'm never tempted to eat them just because I'm bored or peckish. Which means they're there when I really need them. The expiry date printed on them seems to be imaginary, I've eaten them when the foil wrapper is intact but so worn that it's hard to make out what flavour the bar is supposed to be. One subtle advantage is that they're flexible, so you can wedge them into a corner of a bag and they'll conform to the space available. I often shove one in with the rain cover on my backpack and camera bag, so if you carry a rain jacket you could probably put one in that.

In my experience carrying sugar is a waste of time - it just causes insulin surges and makes the whole experience less pleasant. I go from hungry to hyper to hypo to wondering what I just did to myself.

Shopping hint: In response to Daniel R Hicks' comment above, if I'm shopping at a generic chain store that seems to have what I want, I'll buy one each of the more likely options and eat them over the next few days. Or open them, taste them, and bin them if they're not at all what I want. When I find one I like I'll buy 10 or more of them, ignoring the shelf life, and just eat one a ear or so later to make sure they're still edible.

They're manufactured as effectively sterile bar, and they're so energy-dense that anything growing in there will have a hard time unless the package opens and water gets in. Honey and jam work exactly this way - the high sugar content and low water content means anything that tries to grow has the water stripped out of it and it dies.

That's why I still have a stock of powerbars that are probably 10 years old, and I'm not sure how many I have because when I bought a bunch ten years ago I stashed them all through my camping/hiking/touring gear and they still turn up from time to time. It's easy to find an inconspicuous place to carry something, but that also makes it easy to forget when unpacking :)


What are the main differences between road saddles and mountain saddles?

There is a lot of variation across models of saddles even if you stay within one genre (eg only consider road or only consider MTB).

However, you'll find if you look at popular racing saddles that MTB saddles tend to be shorter. This is because in singletrack you're very frequently moving onto and off-of the saddle. A longer saddle might interfere with the "body-english" that some MTB riders use.

That said, if a saddle fits, it fits. That is the most important criteria. Everything else is a distant secondary consideration.


These are wear indicators.
After years of braking, the surface of the rim will grind down to a point that these grooves will no longer be discernable. At that point, you should replace the rim.


i have an se dirt jumper with 4 sealed bearings in the rear hub, can i convert it from QR to solid axle?

If your LBS mechanic looked at it, and said it wouldn't work, why would any of us second guess a professional on a project which can't even look at? There are many reasons I can think of why doing so is a bad idea, even if it works technically.

The biggest reason I can think of for it not working technically is that an axle for a sealed bearing hub has large, machined areas designed to interface with the inside race of the bearing. A solid axle, unless specifically made for that hub, isn't going to be machined to fit the bearing race.

In addition, most axles for sealed bearing wheels are aluminum, which is fine when using a compression closure like the quick release, but which is a poor, and very likely unsafe, material for a threaded closure system like a single speed axle nut.


How to prevent shifting issues due to derailleur or cables freezing in cold weather

Clean and dry (hair-dryer) the derailleur. Relube. Check. If necessary take out the cables, chase the water from the housings by pressing thin oil with a syringe. Put the cables back in or replace with new ones. It's always a good idea to change the cables before winter if you've been riding through rain in the good season. And change them again at the beginning of the good season!


Noticeable clicking from crankset or bottom bracket

There are multiple components that can contribute to a clicking or grinding sound in your drive train in addition to the bottom bracket, including the chain, the pedals, the derailleur and the rear hub. That said, the symptoms you describe seem to indicate a problem with the  pedal bearings or the bottom bracket.

Here are my steps for troubleshooting the bottom bracket:

Pull your cranks laterally. Do they move?
Remove the chain from the chainrings and give your cranks a good spin; listen for any unusual grinding noise or little clicks.
Hold the down tube or seat tube while spinning the crank and see if you can feel grinding or vibration through the frame.

Any of those indicate that you need to service or replace your bottom bracket. That is not a particularly hard task, and if you have been removing or tightening the cranks you likely only need one or two special tools that you may not have. Replacing or repairing bottom brackets is a common task, so it may be worth it to you to pick those tools up. Here are some bottom bracket service instructions:

Cartridge Type Bottom Bracket Service

Cup and Cone Bottom Bracket Service


When a crankset comes loose, stop riding immediately and tighten it. Even going a little distance can ruin the crankset and possibly the bottom bracket spindle. It sounds like in your case, the crankset is toast.

We don't have enough information to say if you need a new bottom bracket or not (the Shimano BB-UN55/56 are standard square taper (ISO) bottom brackets and cost about 10-15 dollars), but you need to combine that with a square taper crankset. Alternatively, you can replace the bottom bracket to another standard rather than square taper (e.g. Hollowtech II) and get other cranksets with that standard.


What skills must cyclists master to succeed at racing?

If you are not familiar with road cycling it may seem like simply a feat of strength/endurance, but there are also a number of skills required.

Skill: Group Riding

Riding in a peloton at speed around corners is difficult.  Often you can be at 65km/hr with 100+ other cyclists around you with only inches to spare while entering a series of corners.  In this situation you often get contact and there is pushing.  You have to be strong on the bike so that you can push back or take a hit without crashing.  This is not easy.  Sometimes opposing riders with deliberately nudge your handle bars in a corner to push you out of position, you need good balance to absorb and push back to hold your position.  You also only have inches to do this before you hit someone else in the peloton and potentially start a crash.

You also need to anticipate how the group moves, if you react too slow you will quickly filter to the back to the group, which is the worst place to be (riders in the back often get yo-yo'd as the group surges and slows).  You will then have to make repeated efforts to get back in or to move up. You can save a lot of energy and effort if you ride smart within the group.  This means constantly making micro tactical decisions.  Over the course of 200+ km race, all these little decisions can mean the difference between whether or not you can put in that last big effort to break from the group and take the win (a la Vino).

Such a constant effort of positional awareness takes a lot of continued focus (our next skill).

Note - I know you said avoid discussion of tactics, but you also said tactics in terms of how the stage is progressing.  Before you can get to that point there are quite a few essential group riding tactics you need to learn.

Skill: Focus

Road racing is about being able to endure pain.  The more pain you can endure the faster you can perform.  There have been points where I thought I was going to have a heart attack because I was pushing so hard. You have to be able focus through this or you will lose your position and potential opportunities.  A good practical example is closing gaps.  Often breaks will get off the front of the peloton and if you want to join you have to jump the gap.  This can be very hard to do when the peloton is at speed.  It requires commitment and focus to sustain the effort needed to get there, as this will typically be an anaerobic effort.

Then once you close the gap you need to focus again on damage control.  You just did a huge anaerobic effort, you can't breath, and all you want to do is rest, but the group you just caught has collectively decided to jump again.  You need strong focus to work through this and stay in the draft of the break group you just caught.  If your focus slips for even a second a gap can form, meaning you will lose the draft and the gap will widen.  You will then either need to do another anaerobic effort to crawl back in (even more focus) or you will fall out of the lead group and get eaten up by the peloton.

Losing focus for a split second at the wrong time in a 3-4 hr race can mean the end to your day. Lets say for example your concentration waned and you fell out of that lead group.  You now lost your draft and are in no-man's land.  The peloton is now fast approaching and actually surges as it catches you.  Before you know what happens you are going straight through the peloton and out the back before.  Now you are off the back of the peloton, with no hopes of crawling back in.  Your day is done, you have just pulled a hero to zero because your concentration waned for a few split seconds.

Other sports such as Baseball and golf also require great feats of intense concentration.  The exact type of concentration differs, but if you cannot focus you will not be a strong racer.

Skill: Knowing your body

This may seems silly to mention, but professional cyclists are incredibly in-tune with how their body functions.  Because races are so long you have to pre-emptively eat and drink.  Waiting unit you are hungry or thirsty is too late, by this point your metabolism will be slowing down and will take time to recover meaning a period of reduced performance. Eat and drink too much and you will feel bloated or sick.  It is a difficult job to know the exact amount to eat and drink and when.  This skill often takes a number of years to hon.

Skill: Being Anal Retentive

Road cyclists are often made fun of for being anal retentive, and it is a deserved title.  That said, it is also a very necessary skill.  Riding a bike is not a "natural" activity.  We didn't evolve to cycle, as such you have to train and practice to be good.  The better the training and knowledge of the finer details the faster you will go.  This can be everything from muscle recruitment (how you activate your leg muscles and core muscle through the pedal stroke), to your position on the bike, to having your equipment in optimal working form (I swear cleaning and keeping the derailleur pulleys in good working order can gain you 20 seconds in a 10km TT).

A strong performance often happens when you get all the ducks lined up (including tactics).  To do this you have to have a little streak (or a lot) of anal retentiveness.


Shimano hollowtech comes in various sizes. The links you posted was for a mountain bike. Mountain bike crank spindles are for 73mm frames, so they need spaces for 68mm frames.

Shimano road crank spindles are for 68mm frames. A BSA (normal British threaded) bottom bracket, doesn't need any spacers, you just thread the cups on and then put the cranks in.

I suggest you watch a tutorial on how to put on a bb and crankset and make sure you follow the manufacturers torque and grease recommendations. When in doubt, get a local bike shop to fit it or take in some food and drink for them and ask them to have a quick look so double check your work.

Also, Shimano have excellent online document on which have all of this information and more. I think your BB and crank should have come with instructions on all of this, unless they've stopped physically including.


What are my options for correcting a bent aluminum fork?

It's not clear what is actually bent. From your picture, it is obvious what isn't bent: your fork is perfectly straight from the crown down to the drop outs.  Also, the boot which covers the stanchion seems to be quite suggestively aligned with the fork; the bend seems to occur at the top of the boot, just before the head tube.  If so, then it is in fact the shock's stanchion which is bent. That part may actually be a steel tube that inserts into the fork's crown. It would help to have a picture with the boot retracted or removed.

Here is what I mean, visually:

If that stanchion tube is bent, then on top of the steering problems, the suspension isn't going to work.  In this case, perhaps just that tube can be replaced instead of the whole fork?

That's the optimistic view. The more pessimistic view is that it's bent in two places. Let's rotate it back along these two points to illustrate:

In this edited image, I've straightened the boot-covered stanchion so it aligns with the head tube. Then a second bend where the crown meets the tube to add caster to the fork.

(Either way, it looks to me like substantially more than a 5-15 mm! That would barely be noticeable in the image. Do they mean 5-15 mm total displacement at the drop-out?)

Like anything else, this requires a careful inspection and diagnosis, so that a well-targeted and cost-effective repair can be performed.


If the lever travel/bottoming problem got worse when you replaced your pads, that's a little unusual.

There is no way on these brakes to adjust the "bite point," otherwise known as lever travel. If it bottoms out or has excessive travel even with fresh pads, that's a symptom of air in the brake line, and the only solution is to bleed the brake.

The pink fluid is Tektro mineral oil. The brake leaking fluid is consistent with symptoms of air in the line. If the fluid leaked due to either the pistons being over-extended, the bleed port being open or loose, hose damage, or a loose hose fitting, it is probably correctable. If it's losing fluid anywhere else for no apparent reason, that's often indicative of a problem with the caliper seals that may not be fixable, since replacement seals for calipers often are not available. There's not really a middle ground situation of a small leak that still allows the brake to basically function. Any noticeable amount will quickly degrade brake function or get the pads contaminated.

At the very least it sounds like the brake needs to be bled. The basic Tektro bleed kit is cheap so it may be worth a shot. If it leaks oil after being bled, cut to the chase and get a whole new caliper or brake.


Welcome to StackExchange.

It's a bit difficult to answer your question without knowing the make and model number of the shifter.  On Shimano RapidFire Plus shifters, used on flat handle bars like you'd find on mountain bikes, the model number is embossed somewhere on the shifter, most likely on or near the handlebar clamp.  Also helpful would be a picture of the shifter with the dust cover removed so the internals are visible.

In absence of more details, I've gotten together a few references for Shimano RapidFire shifter repair/reconditioning.  The Deore XT is this type of shifter, and in 2010 the newest model number was SL-M770.  It's not clear to me what you mean by "reset" so I'm going to assume that your referring to the action of the trigger returning to the start position after each move and click forward. Questions that need answers at this point are, is a click heard when the lever moves foward? Does the lever feel "free" or encounter any resistance after the motion forward?  In addition, are we discussing a right or left side shifter?  A left side shifter would only have 2 or 3 detentes (corresponding to one or two clicks)as it controls the front derailleur, moving the chain between the 2 or 3 chainwheels.

At any rate, the two big things to check: 1) is the pawl engaging the cogs (teeth) with each shift? This toothed wheel inside the shifter should rotate a set amount--enough to bring the next cog/tooth into position to engage the pawls--with each swing of the shift lever (as if you were shifting up the cassete (or multiple chainwheel if it's the front) from a smaller sprocket/chainwheel to the next largest one; 2) is the coil spring correctly engaged in the mechanism--it needs to be placed in the correctly wound orientation and the ends secured in the correct engagement holes. Using the other shift lever (as if to move down the cassette, large sprocket to next smallest), you should note the pawl disengage the tooth and the spring tension that successively builds on shifts up the cassette, release which moves this toothed wheel the opposite way. A crisp click is heard as the pawls engage the next teeth, stopping the spring loaded rotation.  To summerize: note if the shift lever motion translates into rotation of the toothed wheel by the actions of the pawls engaging the teeth of the this wheel, and does the spring appear to build tension (the spring will not have a great deal of movement if seated correctly).  The inference that it was in pieces is not encouraging.  Lotsa small pieces that are very particular as to their orientation and connections inside the shifter increases the complexity as there's a few things to look for at the same time in a problematic shifter that hasn't been disassembled beyond dust cover removal.

Check out these links and edit your question with the relevant details.

RapidFire reconditioning:  http://www.bikeride.com/rapid-fire-shifters/  A basic set of techniques to utilize when first encountering a hinky trigger shifter.

http://thebiketube.com/tutorial/diy-how-quickly-repair-rapid-fire-trigger-bike-shifters. The Bike Tube is a DIY site with this particular link discussing basic repair tips for a trigger shifter.

This youtube video

             is good for observing the correct anatomy of the shifter guts and it uses the SL-M770 as the example.


Trouble deciding between XC and road helmet

My current helmet is the Stratus, and I use it for both road and xc mountain riding.  To answer your question about those two helmets specifically, I do believe they are the same shell with the only difference being the presence or absence of the visor.

More generally, (traditional) road helmets typically provide slightly better ventilation while dedicated mtb helmets offer slightly more coverage for the back of your head.  As Carel's comment points out, mtb visors can also obstruct your vision when riding in a more aggressive road position.  Note that all of these difference are minor and that comfort and fit trump getting the correct "type" of helmet*.

*to an extent - more extreme forms disciplines of MTB require a full face helmet and should not be done with a basic road helmet


remove the wheels
spin the bar
turn the fork 180 to pick up a bit
remove the seat with post
remove the pedals (this is also for damage control)
use boxes for padding
wheels on top
deflate the tires

I think I could get 7 in my 4 Runner but it would be close.

You could even drop the fork and leave the cables attached to put the bar in the triangle.


Matching color bar tape to replace dirty white tape?

According to rule 8, your choices are black, white, or try to match it to the blue frame color, which my be difficult.


To be honest, that might be salvageable.   Slacken the B screw and see if you can pull it down to the normal position.  You will have to remove the chain from behind the freewheel anyway.   This could be tightly wedged in there.

That mechanism doesn't look original - so this may have happened before?

You'll want to eyeball the hanger, then test it with a straightedge ruler, and then gently bend it back to position if its not straight... and if it snaps, you'll have to obtain a replacement.

Second part is "how did this happen?" then "what can be done to stop it reoccurring?"

Often the rear mech catches a spoke and gets pulled around, but in your case it looks like the chain jumped the big cog and is now wedged between spokes and freewheel.

Stop it happening again by adjusting the big-cog limit screw on the RD mech.  You may also choose to fit a spoke protector/dork disk under the freewheel.  My old 5 speed had a classy metal one, but most are clear plastic.

Follow-on damage might include where the chain has munched on the curve of the spokes.   I had this on a MTB and because I pedalled a bit, the chain had bitten halfway through some spokes.  They broke soon afterward, in the next week or so.

Getting the chain out required removing the freewheel/cassette.  You might be luckier if its not as tight.


Are hydraulic disc brakes more sensitive to rubbing with warped rotors?

This is a little bit of a two-layered question.

The literal answer is yes. Given no gap adjustability, if your priority was to avoid rub, a hydraulic brake would be more susceptible to having rub, or more difficult to set up without it, for any given amount of rotor misalignment.

What makes it more complex is that you usually also have the priority of having it be a good brake. Hydraulic brakes transfer power from the lever more efficiently, so for a given amount of braking power output they can have a wider gap. (In terms of their design versus a mechanical.) This is a subtle point because we're not talking about a much bigger gap, maybe not even appreciably, but it's true that it being hydraulic at least moves the needle in that direction.

Mechanical brakes with their pad adjusters and barrel adjusters don't really free you from having to keep the rotor just about as true as true as with a hydro. With most of them, if you back out the adjusters much at all to compensate for rotor warp, the lever is going to be hitting the bar and you won't have much of a brake. It is true that in some cases you are able to adjust the brake in response to slight misalignment and still have it work, albeit with that much more imminence of the lever bottoming.

Different brakes, both cable and hydraulic, also have some variance in how much leverage they employ. The more leverage, the narrower the gap but the more power is generated. The less leverage, the wider of a gap (rotor truth tolerance) you have, but less hard the rotor winds up getting squeezed. There are also various systems that change the leverage (aka mechanical advantage) of the system at different points of the brake lever stroke and/or armature travel.

There are some mechanical disc calipers that are very gappy and tolerant of poor rotor truth, but they're not good brakes. I believe the department store disc brakes are tending to play this trick these days.


Change the angle of the arc of downtube / stem shifter lever to make it an alternative thumb shifter?

Note that there are different levers, depends of the final position. For downtube, head tube or steam, see the ilustration in the bottom of the page:

Some of them have the cable stop vertically, equal as the tube hanger, and other at 90 degrees of it.


How do I tell if I've correctly installed a press fit bottom bracket?

It looks like that Park tool is specifically designed for use on PF30 BB's (+1 for using the right tool). Just curious though, how do the bushings line up with the BB? What surface do they push against? If they push against the inner race, you may well have damaged the bearing. If they push against the outer race or the bearing cup you should be fine. The bearing (i.e. internal race) isn't designed for purely lateral loading.

Are you certain that it didn't have any stiff spots before installation? You can try popping it out and free spinning it in your hand. If its still stiff outside the frame its certainly damaged.

Even if you pressed the bearing cup in completely bass-akwards it shouldn't bind the bearing. The outer race and cup are thick enough that it would take serious damage/force to deform the outer shape of the bearing to cause any noticeable friction.

To address one of the comments: If this is new it shouldn't have any stiff spots. Even the cheapest bearing should spin smoothly out of the box. Putting the crank on will change the inertia of the system and only make it harder to detect these spots.


Unidentified clicking sound coming from front wheel area when performing an endo

Could it be the spokes rubbing over eachother? You can check the tension of the spokes by squeezing parallel pairs together.

My fixie bike makes a clicking noise sometimes when the wheel needs tensioning and I'm pedalling backwards.


Do Bike stores allow you to ship a bike to them to assemble?

I think there are two questions here:

1 - Can you have a bike professionally assembled by a bike shop?  In my experience (having done this a couple of times) it will typically cost the price of their "pro tune" or equivalent - the service when they break the bike down and put it back together.  $2-300 say.  Bike shops can be a bit sniffy about this, but getting to know your local tech staff will help make things easier.

2 - Is this a good idea?  Depends why you're doing it.  If you've got a frame or components you want to put together - say you bought a particular rare steel frame that you want your gruppo from your other bike on...then it can be a great option.  If it's about buying a high-end bike for cheaper - it may be a good option but check where you're sourcing from. If it's about buying a cheaper (say sub $500) bike for less than you can pay in an LBS - I'd say a crazy false economy.  Instead, buy a second hand bike on CL or similar and save $100 or so to get it checked out by your LBS.

Slightly aligned to the point above - if I'm a bike mech, being asked to work on a cool steel frame or a high-end bike from a brand I may never have worked on is pretty cool.  Being asked to spanner a cheap bike from Walmart is going to make me feel pretty crappy about myself and question why I work in the industry.  The level of work I do is likely to be commensurate with how the work makes me feel...


The dimension you need to match is B in your photo. The length of a BB axle doesn't include the threaded ends.
You also need to measure the shell on your bike, though it's probably 68 mm.
See Sheldon Brown for more details.
https://www.sheldonbrown.com/bbsize.html
So a fully specified cup-and-cone type BB would be something like 68x113, meaning it is intended for a bike with 68 mm shell and 113 mm long axle.
FYI: your replacement BB might have threaded holes in the ends of the axles, instead of male threads. (eg Shimano BB-UN26). You'll need bolts to go along with the new BB.


What should I do about salt in V-brakes?

If @ Daniel R Hicks suggestion doesn't work you might need some more intense maintainence. Remove the brake cables from the calipers. Then remove the brakes from the bike, disassemble them completely. Clean all the salt and corrosion from the shaft and the pivot holes of the brake arms. Lightly lube the pivot points and shaft (I am partial to white grease) with a small paint brush. Reassemble the caliper and remount. You may want to do just the front first, that way you have the rear as an example if you get confused during the reassembly. Once everything is cleaned up, a periodic rinse and relube should keep things moving.


Why do men's bicycles have a top tube while women's bicycles don't?

Frames designed for women do have that part - its called a top tube.

Historically women wore skirts, so a lower frame in the middle made it easier to mount and dismount, and was less likely to accidentally show an ankle.

This picture shows a modern "woman's frame" with the top tube paralleling the downtube, and attaching to the seat tube lower down.

Positives:

Skirts
Ease of mounting

Negatives:

Bike is flexier because of fewer triangles
Bike is built heavier to reduce flex

Another frame designed for with these positives is the Mixte frame, where the top tube is replaced by two separate tubes similar to chainstays and seatstays.  These pass around the seattube and terminate at the headtube and the rear dropout, increasing the stiffness of the bike.    They're still heavier than a normal Diamond Frame bike.

Here's a photo of a Peugot showing the twin tubes.

Finally - there's absolutely nothing wrong with a woman riding a DF bike frame.  The main differences now are about proportions, not whether the rider wears a skirt.  There are situations where a man fits a "woman's frame" better than a "man's frame"


90 miles is roughly 140km, so if you're riding that every day it's about 700km a week. Which puts you in elite rider territory for upright bikes without power assist.

It's doable, it's just going to be hard and you'll need to work on nutrition and health as well as fitness. Note that there's also a balance here - if you use world class equipment to get a bit more speed, but need extra recovery and dress/undress time, you might not gain anything. So it might be better (as well as a lot cheaper) to go with elite level gear. I've assumed you'll do that below. You could drop further down that scale, but you will start to lose overall and also the sheer time involved will mean you can only sleep, ride, work (you're already looking at riding 4 hours a day, working 8, sleeping 8, eating 1... that's 3 hours for everything else in your life).

If you're just going to buy a standard elite road bike ($5,000+ and riding kit $1,000+), I suggest joining your local club and buying whatever their favourite bike shop recommends. It will probably help to have two bikes so you can get your weekly service done without having to panic about whether your LBS can get it done in time. Especially initially, you're probably going to need to ride alternate days, and you'll benefit greatly from going on your club training rides once a week or so rather than commuting every day. That way you get training tips and someone to help you understand how your bike works and how to get best use out of it.

One option is to buy a power assisted bike. You'll need to look really hard at battery life, and if you can get a second charger and leave that at work it'll be much easier. I'd also buy two batteries, because 90 miles a day is going to hammer the battery. From your use of imperial units I'm going to guess you're in the USA, which means power limits are hard to predict (they vary haphazardly around the US).

Note that most ebikes and kits are designed to boost low speeds only, and in Europe you can't boost high speeds at all (assist has to cut out at 30kph). So you'll need to shop specifically for kits that will boost you at 20-30mph. Those exist, I've seen a couple of triathalon bikes set up with 500W front hub motors that could cruise at 70kph/45mph for an hour... but those were "money no object" demonstration units at a world solar challenge.

A recumbent is the obvious way to deal with some of the problems. If you choose a fast lowracer or highracer style bike and use bright lights to compensate for the lower profile you will get better comfort and similar speed, assuming your ride is relatively flat. The big win really is comfort - you won't be fighting saddle sores anywhere near as much as on an upright, and you won't be as sore after the ride.

The lowracer style (on the left) is slightly faster in a time trial, slightly slower in a slalom, but you're in a time trial. The main reason to buy a high racer is wheels - they typically use 700c wheels so you can use the wheelset off your existing bike, or buy them easily anywhere. 406 wheels for lowracers are typically harder to find and there's not the intense market contest to get you really nice wheels are a reasonable price.

Combining those two will require a little more work, but a recumbent will probably take a power assist kit better than the road bikes you're looking at. IMO this is the way to go, as you get a small, light, fast bike at a reasonable price (under $10,000). If you did put a kit into your front wheel it would be relatively easy to swap in and out, so you'd only have the wiring and battery mount in place when you wanted to leave it at home.

The no-compromises approach would be a velomobile, possibly with power assist. The Trisled Avatar is designed to go 50kph/30mph using 200W from the rider. Other velomobiles give similar numbers, especially if you pay extra for the fast versions. If you're fit enough to consider riding 90 miles a day, every day you should be able to exceed that fairly easily. That would cut your commute time without compromising your body the way staying in a time trial tuck for 90 minutes would. I believe someone in the USA is doing a 30 mile each way commute in an Avatar. (full disclosure: the Trisled factory owner is a friend of mine).

Trisled don't support electric assist, but there are other fast velomobiles that do. The eWAW is one, but their focus is on helping with stop-start riding so you'd have to talk to them about getting better top speed on long rides. The Avatar is about $15,000 in the USA, the eWAW starts at about 7,000 Euro(google docs link, in Dutch)  but I think the electric version is 8,500 Euro.


What tool do I need to press fit a "Spanish" bottom bracket?

The rather trivial answer is look at the documentation for various bottom bracket presses and see if a bushing set for the BMX Spanish type is available.

For example the Park Tool BBP-1 documentation explicitly specifies that it supports the BMX Spanish type.

If the Spanish BB is not listed you need a press that has an bushing set that works with a 19mm axle and 37mm outer bearing race.

This is the type of task where rather than buy a tool that costs several hundred of dollars it is better to go to your local bike repair shop and have their mechanic do it or go to a bike repair co-op and rent space and tools for the 15 minutes it will take you to press the bearings.


Can I replace chainrings without replacing the rest of the drive train?

The simple answer is yes, you can just change the crankset without replacing the entire drive train however there are other considerations. Depends on if your changing rings out or replacing the set and cranks. Other considerations if doing a full replacement are:

Chain line

When selecting a new crank set you need to ensure it aligns with the current chainline of your bike. If you change the chain line you may not be able to use all of the gears on your rear cassette in all gears up front.

Bottom bracket

You need to ensure that a new crankset will be compatible with your current BB spindle length and interface. (square, octo, isis, hollowtech etc.) If your BB has a lot of wear once you have the cranks off its not a bad idea to change the BB at the same time as they're not that big a cost. Also it's sometimes if you get a good deal on a crankset to get a matching BB as they're the cheaper item.

Chain length

You may need to shorten the chain going to smaller rings if the derailleur doesn't  provide enough tension.

Rear derailleur capacity

Not a problem when shifting to a smaller crankset but if going larger you would need to ensure that the rear derailleur would handle the additional cogs. There are tools online to help calculate this.

Wear

If the chain and rear cassette are showing signs of wear it's often wise to replace these at the same time as they will wear a new crankset faster.

Chain width

If you are buying a new crankset it has to be appropriate for the number of gears on your bike, this is because chains are different widths to accommodate more gears on the rear cassette. The rest of the drive train is sized to fit the chain width.


Are the numbers on a shifter standardised?

No.

The full gearing ratio of the bike (from your foot to the tire contact patch) is determined by four factors: the crank length, the chainring diameter, the cog diameter and the wheel diameter. Since these components can be changed independently, it is impossible to develop a uniform numbering system for a single component ("uniform" in this case means getting the same full gearing ratio from the same gear numbers selected for the chainring and for the cog).

I.e. even if you standardize the "front gear number to chainring diameter" and "rear gear number to cog diameter" relationships, two bikes with different wheel diameters will still perform significantly differently even when the same gear numbers are selected on both of them.


Bike shifts well for low gears OR high gears - but not both

When gears shift cleanly only over part of the cassette, it's often due to the alignment of the rear gears.  If you look directly at the position of the cassette gears and jockey wheels as you shift up-and-down, is the angle not-quite-right when the chain won't shift properly?

Even with a new hanger, if the gear mech itself or the extender has been bent, you might need to bend the hanger out of shape to compensate.  You can buy a hanger alignment tool if necessary (about £65, so not cheap).

Also... is it the smaller gears that aren't shifting?  Is there enough tension in the chain?  If you've bought a new chain, be aware that most are supplied with several extra links that you need to remove with a chain-splitting tool (which costs less than a tenner).

Otherwise, any kinks in the gear cable or grit/gunk in the cable housing could be affecting the cable tension.  It's worth replacing them periodically, and it's both cheap and easy to do.  You'd probably want to buy a good quality pair of cable cutters, though (£15+).

Hope this helps :-)


Are Claris(ST-2400) shifters drop-in replacements for St-2300s?

Yes I test rode a Sora a few years ago with those thumb shifters - truly awful.

My gut feel (I know Shimano well, but don't have direct experience of this groupset) is that one is a direct replacement for the other, but the only evidence I can find to back this is a review on Amazon.

For sure there'll be no problems shifting, because you're staying at 8-speed. I was just a bit hesitant to answer in case something to do with the braking might have changed. But that guy's review suggests you'll be ok - sounds like he did exactly what you're proposing.


What era/country/manufacture is this vintage step through?

This may not be the info you expect, but for your purposes, it doesn't matter at all.
Your mother wants to ride again, and that's fantastically awesome.  Anything that progresses the goal nearer to completion is good.
I suggest you find out if she had a bike in the past, what brand it was, what colour, and anything she remembers about it.  Perhaps conscript any other family to ask on your behalf so its a surprise.
Then paint the bike that colour, or fit a basket if she remembers having one.  Fit an Ahhooga horn if she remembers that.
Buy or make a set of decals that say the same brand as she had, or make ones that say her preferred name,  or even MOM'S BIKE or BLIC for bucket list item completed
You're doing a great job, keep it up.


You are correct that a leant-forward riding position will naturally tend to make a rider support some of their weight with their arms and hands. The more rotated forward the rider is, the more weigh the arms tend to have to support - which is one reason tri-bars have forearm rests.

Good core strength is what allows a rider to take weight off the arms. Strong lower back and abdominal muscles support the torso, taking weight off of the arms. You can try doing some core strength building exercises (which will likely make you a stronger rider and help prevent injury as well).

You should look at your fit on the bike, you may in fact have the bars too far forward and down. Raising and pulling them back may help while you build core strength.


Deore RD M592 with old school shimano trigger shifter

Yes, it will work fine. RD-M592 is designated as a 9-speed rear derailleur. All nominally 7, 8, and 9-speed Shimano mountain RDs have the same actuation ratio.

In theory putting an 8-speed chain through the cage can cause issues, as that's the area that could be sized to want a narrower 9-speed chain, but in practice it never seems to. RD-M592 in particular practically exists to be a nice but not too expensive legacy replacement rear derailleur for 8 and 9 speed mountain bikes, and I've never seen it have issues being used in this capacity.


Cannot fit pump nozzle properly to the presta valve of my tyre

First you need to make sure you have the right chuck setup.  If the pump you have is the one in the link then it claims to be auto-converting between Schrader and Presta -- you can skip to the next paragraph.  But if you have a slightly different pump it may require manual conversion.  As you press the chuck onto the valve you should feel some resistance as the rubber gasket in the chuck snugly fits around the valve stem.  If the fit is not snug the chuck probably requires manual conversion and is probably set up for Schrader, so you need to unscrew the knurled nut on the very end of the chuck and reverse the rubber gasket inside (taking care to no lose any spring or washer behind the gasket).

Regardless of whether the chuck is auto-converting you may need to tighten the knurled nut on the open end of the chuck, to make it tight enough that you feel some resistance from the gasket as you slide the chuck on.

But before installing the chuck you must unscrew the little knurled knob on the top of the Presta valve.  Unscrew it all the way until it stops against the crimp on the top of the threaded rod.  Just to be sure you have it open, press the end of the rod with your finger and listen for the puff of air.

Press the chuck onto the valve.  If the Presta valve does not have a nut retaining it to keep it from sliding back into the tire you will likely need to use your thumb on the tire, on the back side of the valve, to keep the valve from sliding into the tire.

When you get the chuck all the way onto the valve (about 3/4" or 2cm) then flip up the lever to lock the chuck on.  (Note that there have been a few chuck designs where you flip the lever up while applying/removing the chuck, and flip it down to latch instead of vice-versa.)

Once you get the chuck on properly you should be able to read the air pressure (if any) already in the tire.  If not the valve is not open and you will likely not be able to get air into the tire.

Once inflated, remove the chuck and screw the knurled knob down snug (but not over-tight).  And install the cap, if you have one.  This helps prevent damage to the relatively fragile Presta valve mechanism and prevents accidental release of air.

You need to add air to your tires much more often than monthly.  Once a week at the very least, and in most cases 2-3 times a week.


What are the differences between a seatpost-mounted and frame-mounted rear rack

The advantages of seat mounted racks are that they  don’t require rear dropout rack lugs; some of the seat mount racks have quick release levers so you can easily take them off (while racing or transporting the bike, etc), and are many times the only option for a rear suspension bike.

The disadvantages of seat mount racks are numerous:

max luggage weight is limited
many regular panniers that require a bottom (dropout) hook won’t fit
some are designed only for proprietary bags and bag mounts
they are often heavier (thx @michael)
minimum seat drop becomes limited
you can’t use many seat droppers and suspension seatposts as there isn’t enough clearance
seat post damage is possible
doesn’t fit some oval, rhomboidal, or oversized seat posts
if you have a round seatpost and even a modest weight on the back and you take a spill or even do a modest spin-turn, it can be enough for the rack to spin the seat post

Source: had a Specialized hardrock hardtail back in the day and had a regular rack on it. Switched over to a seat mounted rack at one point as I thought it looked cooler and it does, but quickly realized it was most just looks.


I don't have specific experience with this one, but the pictures suggest it works one of two ways:

From where you're at now, you bonk the end of the axle on the non-drive sufficiently hard and the axle slides out, possibly taking the freehub with it, or if not then letting it be removed.
You put the 5mm allen in the drive side end and a cone wrench on the bit with the cone wrench flats next to it, figure out if it's a left or right thread, break that connection and unscrew it, and the hub comes apart that way. I think this is more probable.


If you can create the graphics there are many online services that will create custom stickers or decals for you.

Presumably creating the decal images in the first place is the difficult part. Perhaps you can search for images of the original decals online.


Depends on your location.  Unless there is direct contact or injury you're wasting your time calling the police.    Here in New Zealand we can report a bad driver on the local police website, providing all possible information.     Your jurisdiction may have something similar.

Cameras are "after the fact" information.  They don't stop anything from happening. I've found that a lot happens outside the camera's view.  Behind and beside are areas where bad thing happen.

Personally I've found the best answer to be avoid dying or getting injured.  There's nothing like seeing the problem and avoiding it.

A good loud bellow can be cathartic too, but there's no guarantee the driver will understand or even hear it.  Modern vehicles have excellent sound insulation, to the point where emergency services vehicles can be almost inaudible.

Here's an example of proactive problem avoidance - I did not get doored, and the camera lets you lot enjoy it.

The particularly bad quality U-turn just before this footage was indicative of an unskilled driver, but it was too small to see on screen.  Cameras are not as selective as the human eye at perceiving details.  But post injury/death they could be invaluable to prove what happened, and who was in the wrong.


Are dynamo hubs specific to particular lights?

Speaking in terms of past few decades to current generator hubs and lights, mostly they are interchangeable, with some qualifiers and exceptions.
Almost all current hubs and lights are based around 6 volt, 3 watt, and can all work together. Usually the deal is your hub is going to have its own connector type which it will probably come with, like the two-piece plastic plugs for Shimano or the spade connectors for Schmidt. Your light will either have an integral wire as in recent higher end B&M and Schmidt lights, or terminals for a wire with spade connectors, or in some cases a proprietary plug type with an included wire. It's going to be some type of two-strand wire regardless, which you'll then cut to length, prep as needed and connect to whatever kind of connector(s) the hub takes. Most lights come with wire but not all, and in some cases you'll have choices like getting the fancy Schmidt coax wire, which is excellent but a little more involved to prep.
There are some oddball 12v6w lights and hubs that won't play nice with others, and then there are some random things like the old Schmidt E6Z secondary light that would probably need some creative splicing to work with a Shimano plug, and there's probably some other miscellaneous exceptions. But the reason they're exceptional is that almost all of these lights are intended to be usable as upgrades or replacements on random bikes in the generator countries, and same deal with hubs being intended to drop in on existing bikes, so they're mostly very much intended to be cross-compatible.


On Rim Brakes:

I'd be surprised if you managed to wreck a set of brake pads in a week (or even several hundred miles in nasty commuting weather). Off road riding (MTB, cyclocross, etc.) can chew through a set of pads within a ride or two though depending on the terrain and the technicality of the ride. If they're trying to sell you new pads on a bike (instead of possibly adjusting them), I'd be very suspicious.

You can tell if you need new pads by either (a) the pads have been on there for a few years and the rubber has hardened up and they aren't working or (b) if its due to wear,

new pads look like the top , old pads look like the bottom [the grooves should be nearly gone] (Image from here).

[The bottom pads have a lip on them, which indicates that they weren't aligned properly to begin with. If your pads have just developed a lip, you can cut it off and use the pad as normal after re-aligning the pad.]

If they want to replace the whole brake, then there may be something wrong with the brake that you haven't mentioned (bent brake arm, or something).

On Disc Brakes:
If the bike has disc brakes, one reason why the pads may need to be replaced is if they have gotten oil on them, in which case they do need to be replaced (and the rotors cleaned).

In all cases:
You should really go back and ask them why they want to replace the brakes/brake pads to begin with. Pictures of the situation would help too.


The key to understanding your situation is its unusual nature. Speed on hills is mostly determined by power-to-weight, while speed on the flat is mostly determined by power-to-aerodynamic drag. The problem is that speed in head winds is also mostly determined by power-to-aero drag, so the conundrum is why you're good in head winds but not on the flat under calmer conditions.

If this is truly your problem, the answer is more likely to be the numerator (i.e, power) than the denominator (aero drag). Some riders tend to have more difficulty managing power on the flat than climbing; this is thought to be related to crank inertial load. Crank inertial load (CIL) can be thought of as related to "how much momentum is maintained with each pedal stroke" and varies with the fourth power of gear ratio, so when you're cruising along at high speed on a flat road your CIL is high while when you're climbing a steep hill in a low gear your CIL is relatively low. When you're climbing a steep hill you slow down a lot if you don't keep pedaling pretty steadily while if you're on the flat you can vary cadence or pedal force (within reasonable limits) without much change in speed. The "feedback" you get from the cranks with momentum is the crank inertial load. Many riders appear to modulate their cadence in response to CIL, even at the same power. The last piece of information we need to address the puzzle is that in head winds, people will often gear down lower than they ordinarily would for a given gradient under calm winds.

So, if you appear to do well in climbing and in head winds but not so well on the flat, this indicates that your power production appears to be relatively high under low CIL conditions but not so high under high CIL conditions. If you've ridden much with a power meter you would likely observe that your power is higher and steadier on hillclimbs than on the flat; more than that, you would probably observe that you have difficulty holding high power on modest descents.

There is some evidence that muscle fiber type influences freely chosen cadence so it may be the case that your muscle type is especially canted in one direction that favors power production under low CIL.


Replacing the largest sprocket in the cassette with a larger one?

I was surprised to find that not only did they make this configuration, but it is still made and is available as a 3 speed IGH (integrated gear hub) and a 9 speed free-hub. I have seen older Altus derailleurs similar to the original in the photo used with 28 tooth 7 speed cassettes. I would feel confident in stating that such a set up would work here. A quick search shows a wide range of 7 speed units are readily available. Looking at the photo of the front crank I don't think a smaller tooth front sprocket would be available. The prospect of installing a 3 speed front crank would be a interesting engineering exercise.


What type of chain lube is best for winter riding?

Personally I would go with the finish line wet as opposed to the dry.

Typically I use the dry if I want something that will keep my chain looking clean as well as lubricated. From personal experience I have found that I need to reapply the dry lube more often.

I will use a wet lube, sparingly mind you, for the nastier conditions.

Having wasted your time with that I would say that storage temperature/location, how you clean the chain (method, frequency and intensity) and how you apply the lube (gobs vs. sparingly on each link) is more important than the type of lube.


How do I go about choosing a bike for commuting?

You are asking a lot from one bike - commuting on rough roads, triathlon and cyclocross (CX)!

I would choose a hybrid bike (like a Cannondale Bad Boy, though there are many to choose from) based on the following characteristics:

Larger 700c wheels that make them more efficient/faster than a Mountain bike.
Wider rims and tyre choices that make them stronger than Road/Racers.
Flat handlebars similar to a Mountain bike for a more upright position.
Good range of gears to handle varied terrain.
Often have suspension forks for comfort (though if too cheap, can be more hindrance than help).
When fitted with disc brakes, have good stopping power.

A hybrid bike would be a good fit if the majority of your riding is going to be commuting and comfort is a key driver in your decision. It will be quicker than a mountain bike (assuming 26" wheels and knobbly tyres), though not as fast as a road bike.

A road bike would be faster still, but a more aggressive aero riding position to get used to and you'd probably wreck the wheels riding CX. A CX bike could give you a position similar to the road bike, but is also designed more with racing than comfort in mind. I think CX is a bit more specialised and therefore I speculate you are likely to find less choice and possibly higher prices compared to other bikes of a comparable specification.

You can choose the best tyre width/tread/compound and pressure for the job at hand:

For roads and cycle paths, a smoother rolling tyre inflated to a higher pressure. Possibly some puncture protection if the roads are on the rough side.

For triathlon, you could select narrower slick tyres pumped even harder for less rolling resistance. Perhaps consider some clip-on aero bars. I've seen a right mix of equipment out there - people on very cheap full-suspension bikes with knobbly tyres doing triathlons, but I think they like the challenge and make things hard for themselves!

For CX, you could pick a slightly wider tyre with a more knobbly tread and perhaps run at a slightly lower PSI if you need more grip.

Hope this helps!


After ask for help RST support, I received a brief explanation by e-mail.

"Dear Euller,
Regarding CHAMP travel adjustment, it needs to be adjusted to be part #2.
You must first remove the part #2 from the fork."

I think that is enough to start and open the fork.


I think it will work fine for a while, but the slight angle will increase friction and therefore wear on that point of the cable.  This will make it harder to move too over time.

Water from rain or road spray will rust in there a little faster, and this can result in the housing popping out of the retainer easier.

I'd suggest using some calipers to measure the ID of your mounts, and the OD of your cable, and find a suitable end-cap/ferrule to fit.

Consider asking your LBS - Any good shop has drawers and boxes of little components like laying about.

Another bodge might be to find some thin-walled plastic tubing like garden irrigation pipe and fit a short piece over the chromed ferrule already installed.   I'd not recommend tape as a solution because it tends to mush, and helps hold water.


Rear wheel won't move or keeps falling off

I'm going to say that you have the axle washer on the wrong side, should be inside the dropout rather than on the outside, doing so can stress the disc brake as it was aligned with it (the washer) on the other side, or your simply pushing the frame into the rotational surface so much that it can't move due to the pressure on the entire surface rather than just the axle.
Basing my answer on experience and reading through this

When it's in the wrong spot ( on the outside ) you are also pushing the frame against the surface of the hub which when tightened enough will prevent it from being able to turn. Washers prevent this by adding both space and reducing friction between a moving object and a static one. Essentially a bearing turns fine on an axle but if you sandwich something up against the entire surface of the bearing it wont move due to the friction present on the entire surface area rather than just the axle sleeve.


RevoShift Friction: shifting to the largest gear takes a lot of force?

Some of the revoshifts are actually friction and just don't click period, while others are pseudo-friction (they click in small increments so you can trim your shifts) - I suspect you have the latter. They are also the bargain bin parts (less than 20 dollars for a set), and thus are built with low quality and things often go wrong. Pretty much all you can do is check that the cable tension is OK, the cable isn't caught on anything and the derailleur is set up properly (If the shifter is gunked up, sometimes flushing it with WD40 helps, but thats just a temporary fix).

As suggested in this question, I recommend throwing out the RevoShift shifters if they start to cause problems and then replacing them with some other cheap shifters (maybe switch the left on a cheap thumb friction shifter, or a Shimano trigger shifter with the same number of speeds, or a SRAM Attack front shifter if you want to stick with twist).


Legality of opening someone else's car door?

If you opened someone's car door you could be committing either Dangerous cycling or Careless, and inconsiderate, cycling. (Road Traffic Act 1988)

There's also the offence of Assault to consider. (CPS guidelines)

  An assault is committed when a person intentionally or recklessly causes another to apprehend the immediate infliction of unlawful force.

Aside from the legality question, it's probably worth pointing out that many cars automatically lock the doors once the car starts moving and don't unlock them until the engine is switched off.


Is there a simple way to measure, record, and use wind resistance or tail winds?

Arguably, just the time it takes you to get from point A to point B is a perfectly good measurement of improvement (same with average speed)

As you say, wind influences this, as does countless other factors - traffic lights, weather (wind, wet roads, snow and ice, etc..)

However, unless you are remarkably lucky or remarkably unlucky, these variables will largely average out over time.. E.g a head wind on the way will become a tail wind on the return journey (or a windy day followed by a calm day, or the prevailing winds changing throughout the year)

It's also worth remembering that elapsed time wont just be skewed by negative factors, but also positive things like your bike-handling skills, confidence cornering, confidence at drafting other vehicles etc

The main point is: You should not judge fitness improvement based on specific rides ("todays ride took 2 minutes longer than yesterday") but instead look at trends over time. For example, here is a plot of average speeds for all rides during my first year of "proper" cycling:

Day-to-day it was impossible to see any improvement in speed, it was hugely influenced by factors like the terrain - but, over time there is a clear trend.
Speed and time alone aren't a good indication of fitness

Power output as measured by a device like a Quarq, PowerTap or SRM power meter is far more representative.

Aside from being prone to external influences, increases in speed become exponentially harder. Going from 10km/h avg to 20km/h is far easier than going from 20km/h avg to 30km/h (and then 30 to 40 is even harder)

Part of this is because air resistance approximately increases with the cube of your speed ((ground speed)*(air speed)^2) - in other words, air resistance increases exponentially compared to your speed

I would speculate that the other part is, increasing your power-output becomes exponentially harder the closer your are to your "genetic limit" (e.g increasing your 1-hour sustained power from 100w to 200w is much easier than from 200w to 300w, increasing from 300w to 400w requires far more training)

What does all that rambling nonsense about watts and exponents mean?

If you look at my average-speed plot, there's a large increase in average over the first few months (the easy 10km/h->20km/h increase), then the speed appears to plateau, despite the fact I was increasing in fitness over that time...

This is where power meters become especially useful: It more directly measures a useful metric of fitness, essentially how hard you can pedals for a given duration.

I bought a power meter near the beginning of Dec 2012, where the avg-speed line is quite flat. I knew I increased in fitness since then, however the average speed line doesn't really reflect this.

The best-efforts power curve far better reflects my improvement than avg-speed:

As you can see, despite no large increase in avg speed, my best effort 1-hour power increased from 197w to 254w, which is a substantial change (dividing by 60kg and using the easy-to-misinterpret "watts per kg chart", it's an increase from "moderate" to "very good")

Power meters produce great measurements, but, they are expensive.
There are ways to measure wind speed on a bike, but not for the reasons you describe

iBike sell several versions of a bike computer which measures wind speed.

It's sold for two reasons, the first is to estimate power output without a power meter (the iBike Newton is quite expensive, but cheaper than a direct-force power meter like Quarq, PowerTap etc)

The second reason is if you have a power meter, it can use the power output, ground speed and wind speed to estimate your aerodynamic drag (since your speed on flat terrain is primarily based on power output divided by aerodynamic drag)