Originally Posted by
agmetal
I recently did a 650B conversion on one of my bikes, and I'm a little bit frustrated with the brakes, and I'm curious if anyone else has had a similar experience.
I went from Tektro R539s with 700C Sun CR18s to R559s with 650B Velocity A23s, using the same Kool Stop salmon pads. After some initial concerns about the front brake not being as responsive as it was before, I de-glazed the pads with a file this afternoon, and that didn't seem to make any difference (at least in the front - the rear now locks right up, and I don't think it was before). I also switched the pads between front and rear, and that didn't seem to make a difference either.
I'm pretty confident that the front brake was more responsive before - even using the R559s with the CR18s and the same levers on a previous build (and also with Mavic A119s on another bike). I like the confidence that comes with being able to brake late and stop quickly from the hoods position, and I don't currently have that.
Has anyone else experienced this? Anything else I should try? I don't particularly want to go back to the 700C wheels if I don't have to - the 28mm tires are a little narrow for my taste.
It's not the pads or the rims' braking surfaces. It's primarily a leverage issue. You've significantly reduced the mechanical advantage of the brake calipers by using longer arms to reach your smaller rim. Your new rims require 19mm more reach than your old ones. It's just a guess but I'd say that's probably a 25% reduction in leverage from the brakes for your 622 wheels. The caliper arms on the R559s are probably a little longer above the pivot point than the R539s but I'd doubt they are longer by enough to make up for the increase in reach, especially with the pads at the bottom of the slot.