I sometimes wonder if people who advocate using the rear brake only don't live where there are technical descents. There are number of those around here where you can pick up so much speed between tight turns that braking with the rear only won't scrub off enough speed. Plus, I think you'd end up having to be braking so much you'd risk fade from heat build-up, versus a quick grab of both brakes before a turn that slows you down better, distributes the heat between F and R, and allows the rim(or disk) to cool a bit before the next turn.
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