Why Disc Brakes?

Mountain bikes first used cantilever brakes; next, direct-pull brakes, which avoided the risk of snagging a transverse cable on a knobby tire. But mountain-bike rims are often wet, muddy and warped, making for problems with any rim brakes. Disc brakes have become increasingly popular on mountain bikes and are gaining some popularity for other bicycles.. John Olsen, expert mountain bike rider and engineer (and who supplied the photo at the left here), reports: "When I got my first mountain bike disc brake that worked, the advantages off road were so overwhelming that I changed every bike I had over to them as rapidly as possible.  Hub and rim and spoke design essentially didn't change, except for disc mount provisions on the hubs." For bicycles used on-road, the advantages of disc brakes aren't as compelling. To some extent, they are a fashion statement, imitating motor-vehicle practice. But be aware: disc brakes can't be retrofitted without frame modification. A front disc brake stresses the fork heavily and can tear the front wheel out of the dropouts unless special measures are taken.