Originally Posted by
cyccommute
Usually rim failures from braking are going to show up as cupped sidewall. The metal thins and the pressure of the tire tends to bend the walls out. They can eventually crack and break if used too long.
I have a set of 1980s Mavic rims with untold thousands of miles on them and they are severely cupped. Don’t use them any more as they are on a bike I seldom ride, but have often wondered what would happen when they got too thin. Fortunately never had to find out. Consumable? Definitely.