Originally Posted by
RandomTroll
The rim is obviously concave, to the eye and touch. Concavity is probably the best measure of about-to-failness. The Sun CR18 has 2.5 mm thick walls. Will they both fail at the same thickness? If they both last to 1mm the Alex should last 40% longer. It has a wear indicator. Alex's docs read:
.3 mm ?! They expect me to discard a rim with 3.5mm walls when they're 3.2mm thick? Do I misunderstand or do they make money by selling rims?
Rim wear indicators and early wear/replacement recommendations have nothing to do with selling more rims. It's about lawsuit protection.
The vast bulk of any rim maker's business is from OEM sales, with the total replacement market being tiny. If that tiny segment, the vast majority is because of theft, crash damage, and other wheel failures. If rim makers depended on the few people who rode enough and were lucky enough to have a wheel last to where brake wear is an issue, there wouldn't be a rim business in the first place.
Also keep in mind that brake track wear on road bikes isn't that common at all. The entire issue didn't come to the fore until mtn biking sped up the process to where significant numbers of riders could wear out a rim.
As to whether the thicker rim is all extra wear material, or some more is needed than the thinner one, that depends on the alloy used, and the shape of the extrusion. It also depends on the shape and location of the wear zone, plus whether it's smooth or striated. A thin smooth wear area can survive better than a thicker one with striations or a single gouge, even if it's minimum thickness is greater.