Originally Posted by
randyjawa
True enough but there are other things that will cause this kind of wear.
Pads, themselves, when left to suffer the ravages of time can, and darn well will, become very hard. I learned this the hard way, a few years back. The pads were so hard that they started scratching up a set of near NOS rims immediately. I filed the pads, hoping to remove the hardened surface, but to no avail. The pads had expired, as nearly as I could tell.
Anyway, just wanted to add that and, were it me, the rims will still be rolling along underneath me and my bicycle.
Those must have been some very old pads! Sure, I believe that could happen. Rubber attempts to turn into hard rubber - like a comb - if given enough time. I've never seen them hard enough to scratch a rim myself. They generally stop working long before that.
Most of the time the issue is going to be gravel or other debris stuck in pads. Could also be glass or metal shavings.
To be honest I think a lot of this modern fear of rim scratching seems to be the result marketing. Both the disc brake manufacturers and the bike companies that want to sell you a new bike with disc brakes have an incentive to make people think rim brakes are bad. .