Originally Posted by T-Mar

Most people do not ride their bicycles enough to allow the rims to get to this point. I've only seen this a handful of times and generally there was a big, deep circumferential score from something embedded in the brake pad. However, I have seen several ATB rims which were getting dangerously close, having a pronounced concave sidewall, which is not suprising given the conditions they're ridden in. Commuting would be better, though not much if you're an all-weather commuter. No doubt, disc brakes are the solution for this sort of problem but lacking that, periodic inspection and picking foreign material out of pads will help delay the process.

BTW, great pic for your avatar. Given you location, I assume that was taken on the Charles? We were down there this past October, watching my son's crew win their event at the Head race.