Brake pads gathering aluminium rim debris - lousy rims?
 

I changed my training wheels to Mavic Aksium, 2013 model.
I have to clean aluminium debris from pads every 200 km or so, which drives me nuts.
No issues whatsoever with previous wheels.

I have been using default brake pads from Shimano BR-6800 brakes: R55C4.
I thought debris gathers up because pads have holes from picking out old debris and fresh pads will solve the problem.
Fresh pads, same model, but just after couple of rides the problem is back.

I suspect rims, not pads:
These Aksiums were used by a seller a couple of times since new and then stored somewhere for over a year.
Is it possible, that storing in a moist place might have degraded braking surface ?
Braking surface looks not so good:
http://s3.postimg.org/ezkhdnhcf/DSCF3198.jpg
These dots do not come off, surface is sleek and even, however I don't like their presence on the rim.


R55C4 pads receive positive feedback, so I don't think they cause the problem.
Still, is it possible that it's all caused by unfortunate rim-pad combination?
If so, any suggestions for different pads?

Aluminum rims will get dirty, try steel rims if you don't want this issue (and don't want to stop in the wet)

Have a look here for suggestions http://www.bikeforums.net/bicycle-me...irty-rims.html

I very much doubt that storage has anything to do with the pads collecting rim shavings. Have you tried to sand/Scotch Brite the brake tracks? Andy.

Easiest course of action is to try another type of pad. I have always used cheap rubber pads, usually black - whatever came with the bike or a pair recently bought at the LBS for $4.50. I have never had any of the exotic problems that come up on this forum, including black dirt collecting on the rims. Performance has always been good, so I've never seen the need to upgrade.

There may be an abrasive grit added to the rubber in your pads to "improve" performance. The spots on your rim look suspiciously like galling, and the aluminum dust may indicate accelerated wear.

Did you really post to tell the OP, who notes he is using stock pads, to use stock pads? I know the urge to post a smug condescending reply about the fancy stuff other people use is strong, but you could try reading the post you're replying to first.

Thanks for the critique. Truthfully, do you happen to know the actual composition of the OP's pads? Does "stock" mean they must consist only of rubber, with no "grippy" additives? My post is based on the following:

1. The OP's description of the problem.

2. The appearance of the rims in the picture.

3. My own experience, which is different from the OP's.

I assumed nothing but the above information. Manufacturers understandably try to improve their products. They aren't always successful, and sometimes performance is actually downgraded. Have you never heard of recalls?

It's perfectly safe to resurface them if they get funky like that. Use sand paper, even steel wool will handle a mild case. Mavic actually makes a rim sanding block, it's pretty fine grit though, more for cleaning nasty black brake gunk off.

Also sand/file the brake pads to get the chunks out. For new maybe better pads try Swissstop green pads. I have been using the same set for five years now I think, even through the winter.

I've seen rims like that. Not sure of the cause, but I agree that it may snowball into a worse problem, so I'd be tempted as mentioned to at least knock off the larger looser stuff with sandpaper.

I noticed that one of the rear rims I built up last year (Velocity Aerohead) looks nicely polished. I think I've accidentally dribbled some chain oil on the rim, and it has aided in polishing the brake track.

I've installed a long-pull Origin-8 Classique brake lever with my old Universal callipers, and am well within the skid threshold on the rear, even with a little oil and polishing of the rim.

I can't say I'd recommend the oil treatment, but the rim looks very smooth.

I've had some classic Rigida or Wolber rims that seem to wear rather quickly, so it is quite possible that the alloys and heat treatments are not equal with all wheels.

I do wonder if perhaps the machined sidewalls is a bit excessive. If one gets adequate stopping power with smooth rims or anodized rims, then rough rims would be unnecessary. Although, skid potential in the rear means less baking power is necessary in the rear, and more braking power is required in the front.

the machining of alloy rims with a lathe type device, in order to make them uniformly planar, is the culprit, IME, and the fact that some rim manufacturers don't even try to remove the sharp edges of the ridges that are left behind. eventually normal braking pressure sloughs off shards that get embedded in the brake pads. any brake pad.

good news is that normal braking action will eventually polish the braking surface and put and end to it. bad news is that the shards can, if left embedded in the pads, help to permanently disfigure the rim. IME. and i've had it happen. usually a few hundred miles on a rim is enough to either disfigure it or polish it.

prompt removal of the offending shards is key. i've had occasion to stop in the middle of a ride, a time or two, to do just that.

I don't think the issue od rim material being shaved off the rim and deposited into the pads is any where as simple as some seem to write about. So it's because of the current fashion of machined brake tracks? IME I've seen far more problems with "classic" un anodized or machined rims. It was this issue back in the late 1970s that made me try other pad compounds (and settled on Scott M pads), and there were no machined rims back then. I've seen pad deposits in virtually every pad brand/model that I've sold and serviced. Some like the old Weinmenn orange pads which had significant "treads" were less the others with fuller surfaces. The Campy NRs were the worst of that era.

So when I see this at work on a repair I first pic out the crap and lightly sand or file the pad and the rim. If there's a repeat I replace the pads. So we feel that this is NBD. We clean things up, readjust/replace and move on.Andy.

I get a certain amount of black goop on my bike, but my rims don't seem to be wearing down at any appreciable rate -- this has gone on for years. I'm guessing that the actual amount of aluminum is miniscule compared to the amount of mess that it creates.

Now I've found real shards in brake pads, due to a small manufacturing operation in my garage creating aluminum chips. I've tried to be much more tidy since then.

Try Swissstop BXP blue pads:
BXP | SwissStop

Ditto, exactly the same problems with my Alex Z1000 rims and stock brake pads. The rims are scored, I have to use Scotchbrite pads and various cleansers every week or two on the tenacious blackening to keep the scraping noise to a dull roar, and periodically have to pick out bits of aluminum embedded in the brake pads.

I haven't tried emery cloth or polishing the rims yet, but might if I get better pads to start with a clean slate.

However I will say there's no problem stopping. It's just noisy and rough feeling every few days to a week, depending on how often I ride.

The tip of a sharp knife blade is helpful in picking out the embedded chunks; the sooner they are removed the better.

I've had this issue with Shimano pads on at least three bikes over the years. No issues after switching to Kool Stop Salmon pads.

As mentioned some pads are better than others at preserving your rims and still stopping well. I've also found that the KoolStop Salmons or the Swisstop Greens seem to be less abrasive and collect fewer shards especially in wet conditions. Haven't tried the newest Swisstop Blue compound but they may be pretty easy on rims too.

I'd be concerned about anything that is apparently abrading the rims, even making tiny gouges in them. If the pads don't contain an abrasive additive, then what's causing the wear and pulling up bits of aluminum? It could just be rubber pads plus heat, but I wonder if something else is involved. Road grit may be getting embedded in the pads and doing the damage. Maybe some pads pick up and retain more road grit than others.

BTW, @Nerull, this isn't a rant against "fancy" equipment, as if any brand of brake pad could break someone's bank account. As always, I'm just interested in finding a solution to a mechanical problem. Whatever people want to spend on their hobbies is their own business. Sometimes cheaper is better, sometimes it's lousier. It all depends on the experience.

I had that problem with a set of OEM Alex rims. I eventually figured out the problem was poor machining on the rim brake surface. The solution was to carefully sand the surface with about 120 grit sandpaper. I could see fairly large aluminum particles coming off. The rims have been fine ever since.

The answer !!!

Those pads are softer. They stop better, especially in the wet. But, being softer wears the pads more and the wheels less. This will reduce rim wear as much as anything possibly can. But you still need to check the pads once in a while. If you always ride clean dry roads, it's not much of a problem. However if you ride off road, or ride in the rain, the rims and the pads will wear faster. Nothing you can do to completely stop the wear.

I have at least five or six bikes with the Kool stop salmon pads.

I agree. Despite the difference in pad composition, I find that the pads last thousands of miles anyway - even on my commuter bike that gets ridden in the rain regularly. I rarely ride off-road, so no experience about how that affects pad life.

Yes, KoolStop salmon pads are good.

Some years ago, I smoothed a machined brake track with 400 or 600 grit wet-and-dry sandpaper. Fold a small piece to the width of the track, wet it, hold it steady next to the brakes for support, and rotate the wheel. The goal was to remove the high bits of the machining, not make it all perfectly flat and mirror smooth. Some remaining pits or grooves are okay.

Aluminum rims are really soft metal. It's too easy to sand a depression into the brake track if you use a rougher grit and sand one area at a time. I think 120 grit (or a file!) is way too rough for good control.

Yes, aluminum is a soft metal and it would be easy to remove too much material if you try to sand out the grooves. The other problem is that unless the bike is never ridden, gouges and grooves are going to occur any way. Sanding them out every time one appears is eventually going to wear out the rims more quickly than they would normally.

As to aluminum bits being embedded in the pad, that's not going to cause much problems. Aluminum on aluminum is going to wear both about equally. The real problem is when a piece of sand is embedded in the pad. That's what causes the gouges and grooves in the first place. Sand...which is quartz...is harder than even steel. Removing the sand is more important than removing the aluminum.

My thoughts exactly. I wonder if some rubber compounds (probably softer ones) attract and hold bits of silica from the road more easily than others? I just removed the rear pads (Shimano, long oval shape) from my bike. Found one tiny depression in line with a fine groove on the rim. Whatever was in that depression was gone, but it must have been hard.

Thanks guys for the input.


not the case with my rims, unfortunately.
I thought the problem will cease when I begin a "clean slate" with fresh pads, but it didn't happen, so I got mad and posted here.


I polished the braking surface with P80 sandpaper. Not a fresh piece, so the 'effective' grit was a bit smaller. Place by place, not by rotating a wheel while holding sandpaper next to it.
I wish I had waited for posts regarding grit and rotating technique.
Fortunately, I was gentle enough not to create any depressions in breaking surface - it's even and true.

I wanted to wait with posting until I can say anything about the results,
but the weather outside looks like the indoor trainer season has started for real,
so it might be difficult to get enough rides outside anytime soon.
Will drop a line if that changes.

I've never found a piece of sand embedded in a brake pad, only shards of aluminum, which WILL gouge up the rim with continued used. If you can hear grinding, it's grinding! (I HATE that sound!)

Yes, picking the bits out of the pads asap is smart, but stopping in the middle of a ride isn't always convenient. I just avoid using the offending brake while finishing up the ride. (unless needed for emergency, of course)