How fast do carbon and aluminium rim brake tracks wear?

Question

Rim brakes wear the wheels' brake tracks. How long do wheels usually live until they're worn (In terms of distance, not time)?

Of course I realise this depends on how much I brake, not how much I ride. There's only a somewhat loose relationship between the two. It probably depends even more on how dirty brake tracks and pads are.
Still, I roughly know how many km I ride my bikes, but I've no way to track braking. For example, I've worn two aluminium front wheels, one after around 20_000 km, the other after around 70_000 km.
When getting new wheels, it would be great to have an order-of-magnitude expectance.

Is there a general difference between wheels with carbon / aluminium / steel rims?

Answer 1

The materials you quote are quite different. Even between different types of aluminium rim, wear rates can be significantly different. A set of wheels I built with high end aluminium rims were ridden 30 miles, 5 days a week over a very hilly, windy, wet area and the rear rim was dead in 6-9 months. We replaced the rim with a different type and got almost 2 years out of similar conditions. Meanwhile, the ceramic coated rim I bought used and had on my mountain bike, and used hard, isn't worn at all in the conventional sense. That one did 10 years work with me and was already over 10 years old when I bought it. I stopped using the wheel when I went for disc brakes.

Carbon rims are somewhat different in the sense that very soft pads are chosen to minimise harm to the rim (generally) plus they are often deadly to use in wet conditions (applies especially to older types) and are so expensive (were so expensive) that people would usually onlyuse them for race day and occasional fine weather training rides. So the wear rate is much harder to discern.

There's no real answer to your question: If you live in a flat area where it's always dry, your rims will last forever (or close enough). If you live in wet hills where there is always grit washed off gravel sideroads and each downhill finishes with a hairpin/switchback, you'll get less than a year out of your rims, ridden everyday and maybe the same in the city.

Answer 2

Wheel rims live a very long time, but are still consumables when used with rim brakes.

If they're not damaged, braking will wear out a rim in 20,000km ~ 100,000km in my estimates.

The back wheel wear is accelerated by being dirtier, so the rim has more abrasive grit on it which is collected by the brake pad and pressed into the rim, acting as a grinding dust.

The front wheel's wear comes from doing 90% of the braking effort.

You can extend your rim's life by

1. Inspecting the pads every 1~3 months, and using a pick to extract any embedded debris in the rubber. You'll be surprised how many flakes/shards of metal are in there, and they're all scoring your rim at braking time.

2. Wiping the rim clean periodically. If you rub a clean finger on the rim and see a dirty mark on your skin, then a quick wipe around with an old rag will improve your braking. Do both sides, and remember the sector of wheel that is under the caliper/stays too.
   This is more important in winter when the roads are just dirtier.

3. Avoid riding through deep puddles where you can, and store your bike in the dry After a severely wet ride, give the rims a wipe down.

These tips will help you extend your rim-brake rim's life.

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High load does not wear out a rim, but it may increase the chance of going out of true or splaying the sidewalls.

I have hit a pothole hard which popped a rim weld on the rear. I forced it back into line, but the result was a tiny step for the brake pad to go down, which ate a brake pad in a couple months.

Steel rims last much longer than aluminium, but noone really uses them for weight reasons, and aluminium rims have far superior braking performance in the wet.

I can't speak for carbon fibre rims, have never owned one.

Answer 3

That totally depends on the road, weather and brake pad quality.

In dry weather, you can expect aluminum rims to last so long that your wheels fail by rims cracking around the spoke holes (which is why you should use double eyelet rims to extend spoke hole life) and not due to rim brake track wear. However, if you have a poor brake pad and make even one mistake of riding in wet weather, abrasive debris will find its way into your brake pad. It stays embedded there, so for all your future dry weather riding, you can count on the brake pad working like sandpaper. The fix is to either use sandpaper to remove the surface layer of the brake pad away (shortening its life by the removed surface layer), or to switch to better quality pads. As far as I know, there is only one brake pad type available that does not suffer from this embedding grid effect. It's a brake pad that contains iron oxide additive. It's rust-colored (has to be, no other color is possible, as rust makes it orange). As far as I know, there is only one brand that makes this iron oxide pad and it's Kool Stop Salmon (feel free to edit if some competitor finally realizes that iron oxide is good in brake pads!).

In wet weather, all pads, including even Kool Stop Salmon, grind the rims away. The difference in pad quality is only whether the problem goes away when the rain goes away, or whether the grit stays embedded in the pad forever.

Also flatland riding vs mountain descents (little braking vs lots of braking), and countryside riding vs city riding (little braking vs lots of braking) affect whether rims wear slowly or quickly.

I think the lowest limit for rim wear is about "10 wet mountain descents": https://yarchive.net/bike/rim_wear.html ...which might be as little as 500 km.

Highest limit? Maybe if you never ride in the rain, 100 000 km is possible unless your spoke holes in your rims are already cracked by then. With double eyelet rims, 100 000 km might be possible.

Answer 4

I've had some Campagnolo Bora carbon wheels for about three years and there seems to be hardly any wear on the brake track. Granted, these are fitted to my weekend warrior bike but I do have aluminium winter wheels (Fulcrum Racing 5s) and their brake track is showing signs of wear. I do care for these wheels though, only use Campagnolo Bora brake pads and clean the wheel and pads regularly.

I used to commute to work by bike for about five years and was doing about 3000k per year; I was getting through alu rims every 12-18 months! I know it's not a fair comparison but carbon rims do seem to be more durable when used with the right pads.