Bike Maintenance & Repair Clinics

As first year riders, we're required to attend a repair clinic, so last night, Stu and I attended one at Velotique. It's a neat little bike clothing and accessories store located at 1592 Queen St. E. Their slogan is something like "the best selection, because we don't sell bikes."

This seminar was given by Saul, and if you've ever seen a Velotique catalogue, then you'd recognize him. While his store doesn't sell bikes, they also don't do bicycle repairs. Saul says that the best mechanic for your bike is you, and that's something I've always believed as well. No one else is going to want to put in the time to adjust things properly when they're not the one riding the bike. You see this all the time with new bicycles - the gears and brakes are almost never tuned properly. I suppose when you work in a bike shop assembling bikes all the time, you eventually start to take shortcuts.

The clinic covered three topics: preventing and repairing flat tires, cleaning and lubricating your chain, and adjusting the rear derailleur (which is the thingy that shifts your gears). I've been tinkering with bikes since I was around 12 or so, so most of this was old hat, but I'd never been taught any of it in person, so I did pick up a few things here and there. In particular, there were 2 things I learned that really stand out.

1. Gauging chain wear.

   First the short one... you can check for chain wear by shifting onto the large chainring, then pulling the chain forward and checking how much slack there is. If you can expose a full tooth, your chain too worn. Chains sort of stretch over time, so that the links don't line up well with the teeth on the gears any more, and this can cause jumping and poor shifting. If you ride with a worn chain for too long though, the gears will wear as well, and then a new chain will not work properly with the gears. So it's best to replace chains before they wear, because chains are cheap and gears are not. Saul recommended doing it every year, but surely it depends on how much you ride. I've never changed mine, and it's only about half worn out.

2. The importance of tire pressure.

   Air pressure is often measured in pounds per square inch, and that relates directly to how much surface area of the tire is contacting the road. With skinny road bike tires, typically about 1 sq. in. per tire should be in contact with the road. In the past I've inflated my tires to about 100 psi, which means that the bike can carry 200 lbs of total load, rider and bike (though this doesn't take into account impact forces, like riding over a curb or hitting a pot-hole). If you go beyond that, the tires squish down until the area of contact is large enough for the pressure to support the weight. In extreme cases, this will pinch the tube between the tire and the rim, causing a flat.

   Even with my bike, I'm nowhere near the 200 lbs that my tires can support when inflated to 100 psi. However, tires lose air over time. A car tire is large and has low air pressure, so it doesn't lose air very quickly. A road bike tires is under high pressure and contains very little air, so a small amount of air loss makes a big difference. I usually try to pump my tires up before every ride, but sometimes I'm lazy and I don't bother if it hasn't been too long since my last ride. Often when I pump them up again, I notice that the pressure is down to 65 or 70 psi, which is not enough to support me and my bike without significant deformation of the tire. In addition to elevating the risk of a pinch flat, this adds rolling resistance which slows you down.

On Tuesday, the day before the repair clinic, I decided to fix my flat tire because I knew I wouldn't have much time to do it this week before the next training ride on Saturday. Since I speculated in my last post that my worn rear tire had something to do with it, and since I refuse to ride with mismatched tires, I bought a new set of Schwalbe Stelvio Rain tires. (I didn't realize at the time that they were made for riding in the rain, but that's a pleasant surprise, because rain does make me somewhat nervous about slipping.)

When I inspected the tube, I didn't find any glass or anything sharp, but I did find that it had not one, but two small punctures, one on either side of the tube. This had me utterly confused. Had a needle somehow gone sideways through my tire? Had I run over a staple? Well, I learned at the repair clinic that this is known as a "snake bite" and it's exactly what happens when you get a pinch flat. So it turns out that it was the pot-hole that killed my tire. Since it was rainy, I couldn't swerve, so I just rode straight through it. I think my tires were inflated to about 115 psi that day, but from now on for that extra bit of protection against pinch flats, I think I'll aim for about 140 psi before every ride, if my pump can handle that (and if not it's probably time for a new pump too). Saul recommends inflating to the maximum recommended tire pressure that is printed on the sidewall of your tire, which is 145 psi for my new ones.

I'm excited for this Saturday's ride! I've only ridden around the block with my new tires, so I'm eager to see how much faster my riding will be when my tires are pumped up to 140 psi.