bemoore

I have a old (mid 90's) Raleigh M50 MTB with Alivio cantilever brakes. It's been converted for commuter use, but that really hasn't seemed to have any effect on this problem which has occurred since it was new (and used only for mtn biking).

The problem? Debris gets on the pads... which grinds into the rims... which causes aluminum to grind off & get embedded into the pads... which grinds into the rims....
A few times, I've done the following:

- Dig out the debris, aluminum, etc from the brake pads.
- Dremel off the glazed surface of the pads.
- Sand the rim by hand until smooth with 400 grit sandpaper
- Clean rim w/soap & water

This seemed to work very well... until more debris got onto the pads, and started the process over again. It seemed to only take one trip through a puddle to initiate this chain. The problem I have is with the sanding of the rims. I'm not sure I'm doing it right, or if I should be doing it at all. It takes me a long time to get the braking surface smooth (relatively... I'm not going for perfection). One time I tried NOT sanding the rims, and just doing the above process to the pads, and then cleaning the rims. This helped, but it seemed that the rough surface of the rims flaked off aluminum, and quickly fouled the pads again. So it seems that the rim sanding is necessary. So, the question becomes... what is the best way to do this? Should I start with something more coarse than 400 grit? What grit should I end with to get the right roughness? How do I get a nice, flat, smooth surface on the rim? Using just 400 grit sandpaper takes me about an hour per rim. Then I have to service the pads, and clean the rims. I can do a brake job faster on my car. There has to be a quicker way.

And as a general rule, is this a valid procedure? I also have a 2004 Trek 1000c, and its brakes grind occasionally, but not nearly as bad. How should I go about fixing this problem on this bike? From my searching here, it seems that the recommended procedure is to:
- Remove debris from pads
- Make a swipe or two with a flat file to de-glaze the pads
- Clean rims with Scotchbrite pads and possibly a solvent like mineral spirits.

Thanks.

zzyzx_xyzzy

If it's happening over and over you might have better luck with different brake pads. Shimano pads seem to be pretty bad for turning themselves into lathe bits. Kool-Stop are better.

I would skip the sanding the rim part. Just clean them (alcohol seems to work better than mineral spirits for me)

BCRider

Aluminium doesn't ball up and get into the pads unless it's galling. Dirt in the pads will not do this. But the poor choice of pad material that Shimano seems to stay with will do it all by itself. I'm betting you have the original Shimano pads or some Tektro stock pads. Both are extremely bad for those of us that weigh over about 160lbs and thus need to use more force on the brakes to stop. Nothing you do to the pads will correct this.

Ditch those pads and get some Koolstop Salmon pads. You'll be able to use less lever force for the same stopping and your rims will actually get smoother and nicer with use... well, up until they eventually wear through. But that's going to happen anyway. When the Koolstops get gritty from riding in mud or rain the pads clean up with just a good scrub with a coarse rag and soapy water.

bemoore

OK. Koolstops it is. I have those on my road bike, and I like them.

Thanks.

Ira B

Koolstops are good.
Also, automotive brake parts cleaner works great on rims and pads, just don't spray it directly on.
Spray it on a paper towel then wipe the pads and rim sides.