Originally Posted by
Mr Pink57
I would be all for discs brakes in road riding. My all arounder that does road duty does in fact have discs brakes 160mm f/r bb7s and do like the stopping power.
What I find odd that discs brakes are not on a road bike is this is probably the fastest category of biking, yet probably use the simplest brakes.
Road bikes have appalling traction: just compare riding a road bike and a slicked MTB on a fast bendy downhill. Braking power past the traction limit is good only for making skids.
Also: don't be so sure that road bikes go faster than descending MTBs.
Nerull:
When the brakes you have are quite capable of throwing you over the handlebars, is more braking power really what you need?
If the brakes on a road bike can throw you over the bars on the flat or a reasonable decent, then you're braking wrong:
http://www.sheldonbrown.com/brakturn.html
Jobst Brandt has a quite plausible theory that the typical "over-the-bars" crash is caused, not so much by braking too hard, but by braking hard without using the rider's arms to brace against the deceleration: The bike stops, the rider keeps going until the rider's thighs bump into the handlebars, and the bike, which is no longer supporting the weight of the rider, flips.
This cannot happen when you are using only the rear brake, because as soon as the rear wheel starts to lift, the rear wheel skids, limiting its braking force. Unfortunately, though, it takes twice as long to stop with the rear brake alone as with the front brake alone, so reliance on the rear brake is unsafe for cyclists who ever go fast. It is important to use your arms to brace yourself securely during hard braking, to prevent this. Indeed, good technique involves moving back on your saddle as far as you can comfortably go, to keep the center of gravity as far back as possible. This applies whether you are using the front, rear or both brakes. Using both brakes together can cause "fishtailing." If the rear wheel skids while braking force is also being applied to the front, the rear of the bike will tend to swing past the front, since the front is applying a greater decelerating force than the rear. Once the rear tire starts to skid, it can move sideways as easily as forward.