Originally Posted by
HTupolev
Depends on the region. Partly because of road and traffic design affecting the amount of required braking, partly because of an area's climate and chemistry.
The Seattle area is perpetually covered in a fine dust that never gets fully cleared from the roads, and which turns into a nasty abrasive when wet (and the roads are wet a lot here). I had one interesting comparison, two rims of the same model line, one on a bike that got used only in sunny weather and another on a bike that I was using near-exclusively in wet conditions: after around 1500 miles on each, the sunny-weather rim still looked new, the rainy-weather rim had very obvious concavity, and had burned through a hefty chunk of its safe usage life.
That was a fairly cheap rim and probably wearing faster than most, but it's not an unusual theme. Everybody who rides in the wet here is familiar with the situation. And yeah, there are people who burn through rims on a two-year cycle or faster, especially commuters.
I've also been in the room when the rim on someone's rain bike exploded due to brake track wear while airing it up before a ride. That's an extremely violent event: along a stretch of the rim the hooks separate from the rim base, there's a sound like a gunshot, and the tire blows off. If that failure had decided to happen during the ride, the fact that the guy hadn't checked his rim wear in a while could have resulted in serious injuries to himself and others (especially since it was on the front wheel).
Seattle gets on average 38 inches of rain a year. Seattle gets on average 4.6 inches of snow per year. Pittsburgh gets on average 38.3 inches of rain per year. Pittsburgh gets on average 27.7 inches of snow per year. Seattle doesn't have a lock on rainfall. Oh, the national average rainfall? 38.1 inches. The national average snowfall? 27.8 inches, so Seattle is actually below average when it comes to total precipitation when you factor in snowfall, and just average when you look at only rainfall. You also don't have a lock on dirt. Talk to the people in West Texas about your fine dust and they will laugh at you. They have sand, and sandy windstorms. I lived in Odessa a while. At least 1500 of my mikes on my current rims have been spent on crushed limestone, very abrasive, and it gets all over the bike. Add to that the abrasive material put down to combat snow and ice, and there is more abrasive material to affect the rims. Not surprisingly, the rims are still okay.
Did you wear your rims out in 1500 miles? Yes, I believe you. Is that the norm? No. Is two years the norm? No, otherwise the bike industry would have moved away from rim brakes years ago out of outright need, and user frustration at having to replace rims so often.
The argument that rims have to be changed every two years, in regards to someone asking about a rim brake model frame he is having trouble finding is ridiculous. It is like anything new. Oh my gosh, the old stuff'll kill you! You will be risking death and serious injury with those rim brakes! You will never survive. Update your will!