Monday, March 16, 2009

Disc Brakes

I was cruising some old posts the other day (about DIY wheel truing stands) and ran into a ridiculous comment that someone made about disc brakes. I'd take apart the whole thing, but instead I'll just talk about all the things that make disc brakes better than rim brakes.

First and foremost, when you use disc brakes you are not damaging anything on your bike. When you rip down on disc brake lever you are applying an mixture of metals held together with a resin (your brake pad) to a piece of steel (your rotor) that was designed solely for braking. I haven't ever seen a rotor that was worn out, but I'll keep looking. On the other hand, when you clamp down on your rim brakes, you are applying a rubber pad which may or may not be coated with whatever muck you have been riding through to you rim, which is probably made out of aluminum. Sure it is as easy to replace your pads in either system, but I have seen several wheels that needed to be replaced because the rim's braking surface was shot. If you are running expensive wheels, this is nowhere near ideal.

Second, despite what anyone has told you, properly adjusted disc brakes work better. If you need proof of this, look around at what professional cyclists use. Have you ever seen a modern downhill rig built with rim brakes? If it was all just some marketing gimmick, don't you think someone out there would stand up and build a rig with rim brakes? Trust me, someone out there would, if not for the simple fact that disc brakes actually do have more stopping power.

Hydraulic disc brakes are definitely more complex, however, they take one of the major points of failure out of braking, the cable. Cables stretch, they frey and eventually they rust or break. While hydraulic brakes have their own draw backs, I have found that a good set of hydraulic disc brakes are easier to install and properly adjust than a set of high end rim brakes. And barring crash damage to the brake line, they last longer and stay in adjustment better than a set of cable brakes (disc or rim). I have a set of Formula Oro Puros that have been on my bike for three years. I have never bled them, never replaced the pads and they are still going strong. They are by far the best part I feel I have ever bought. The most I ever have to do is a quick adjust when I swap between wheel sets, and that generally only takes a couple minutes. I can't even imagine the hassle I would be dealing with switching between 25mm and 44mm wide rims with rim brakes.

Many people claim that rim brakes are lighter than disc brakes and I have to give them that on average they are right. However, if you are willing to pay for it, there are several companies out there making very light disc brake setups. By contrast, as the rim brake market is shrinking, companies are putting less time and energy into development of lighter rim brakes. Thus, rim brakes are tending to stay the same and disc brakes are getting lighter every year. In fact, I think that if you did the numbers, you'd find that a high end set of lightweight XC style hydraulic disc brakes are about the same weight as a set of Shimano XTR rims brakes. The caveat that many people overlook is that you have to use a heavier rim with a braking surface than you do with discs.

The main drawback of disc brakes is that they are expensive. Many people don't need the extra stopping power that they provide. You average summer commuter or pleasure rider definitely doesn't need them. But for anyone who is looking to do actual technical riding or winter riding, I think they are a must have.

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