Why are my rims shedding bits of alloy?

[NewHorizon]

My newly acquired DRC ST19 rims on my road bike are causing me some alarm; the rear one seem to be shedding an alarming amount of alloy filings. After one brief downhill on Sunday I had to stop and remove two lumps which had built up in the wear groove sufficient to make a clunk on each revolution as I braked. The pads are the Shimano ones supplied with the XT cantis - I'm having to take them off every week to dig out all the lumps, which are scouring the rim and no doubt exacerbating the problem. These are the first rims I've had with this continuous wear groove, and I don't like it - it seems overkill, it reduces the braking area and allows bits to get stuck. Should I move to softer pads or will they be shredded in double quick time? This is my Sunday best bike and its washed after every ride.

[garygkn]

I had a similar thing happen with Mavic touring rims and I swapped out the Shimano pads for Kool Stop pads and the problem seems to have gone away.

[Halla]

Have had same problems with Mr S's brake blocks. One large bike shop in Harrogate has stopped selling them because of this problem.

[Kevin K]

I've got DRC MT19 rims and noticed the same problem last time I did a clean and service. I'm not using Shimano blocks, but I might try changing the blocks for Koolstop all the same. Kevin

[epa611]

I have DRC19's and Koolstop pads and have no issues

[andrew_s]

Some makes of brake block do chew bits of aluminium out of the rim. Shimano are well known for it, but there are others which I shan't mention because I'm not all that sure which they are. Koolstop are OK, and I think Aztec too.
If you persist in the use of Shimano blocks, you'll find that your rims wear out relatively soon (6,000* miles/8 months in my case, before I switched to Koolstop).

* not as long as the tyre that went on at the same time

[NewHorizon]

Its odd that it affects the rear far more than the front - I put some Koolstops on the front for better braking to eliminate fork judder and they squealed blue murder so I took them off again! Will now try them on the rear. You'd have thought that after 100+ years this sort of thing would have been sorted by now ...

[vernon]

Shimano blocks are well known for their abrasive properties.

I use Koolstop Salmons and have good braking and minimal rim wear.

[Kevin K]

Since my post above I have changed my brakes to Shimano XT and in just a few weeks the standard blocks are eating my rims. I will be changing the pads to Koolstop or Aztec this weekend! Kevin

[CREPELLO]

If you don't have Koolstop blocks yet or can't afford them you can go some of the way of improving your existing ones by making a toe at the trailing end like the koolstops. Take a sharp knife and make a cut about 8mm into the end of the block, using the block holder as a guide. To permanently alter the angle of the toe (so the end sticks out about 2mm's) spread the toe apart with a temporary wedge and fill the thinnest end of the gap with superglue. Not too much though - you want to try and maintain some give in the toe.

I think the toe feature is a much responsible for Koolstop's reputation as the compounds they use.

[JEJV]

I've seen this as well with Shimano S70T pads supplied with Deore V-brakes.
Also - to a much lesser extent - with Clarks CP510 Thinline ATB blocks. Which is annoying, as I liked the feel of the Clarks pads.
Again, no problem so far with kool-stop dual-compound (Haven't tried salmon yet).


However, I've noticed that the bikes we have which /don't/ have machined rims don't seem to get this problem (Comparing Clarks pads).

The OP's DRC ST19 rims are machined, AFAICT.

Has anyone seen this swarf pickup on non-machined rims ?
Or has anyone else been able to make the same comparison with machined/non-machined rims ?