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Permalink Reply by Barry Niel Stuart on December 14, 2012 at 10:01am

Do your pads bolt on or do they slide into the shoes?  If they slide in, there will be a small retaining pin at the back of the shoe.  My own touring bike has salmon colored Kool-Stop pads, which I've found to be easier on the rims than the original black Tektro pads that came with my bike.  I like them better than the Shimano pads thatr are a common replacement.

 

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Permalink Reply by Rich S on December 14, 2012 at 1:46pm

They're the bolt on pads. I just took my wheel off and dug the bits out with a flat screwdriver. There were only 2 on one of the pads. 

Barry Niel Stuart said:

Do your pads bolt on or do they slide into the shoes?  If they slide in, there will be a small retaining pin at the back of the shoe.  My own touring bike has salmon colored Kool-Stop pads, which I've found to be easier on the rims than the original black Tektro pads that came with my bike.  I like them better than the Shimano pads thatr are a common replacement.

 

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Permalink Reply by David S. Kato on December 14, 2012 at 5:34pm

in my experience, it happens when the rims are aluminum and the anodization has worn off.  it seems to be worse when riding in the wet.  

my theory is that somehow the brake pads pick up some speck of dirt. when you apply the brakes that speck of dirt rubs against the rim, which abrades the rim enough that the rim 'dust' clogs the brake pads.  once it starts happening, it gets bad fast; the speck of dirt quickly becomes a mound of aluminum in no time and gets impacted into the pad.  the only remedy (if you can call it that) i have found is to routinely pick out the impacted material with a dental pick (or similar--i guess a screwdriver works, too).  

it doesn't seem to happen as much to those rims with anodized sidewalls.  possibly a change in pad material will affect how quickly it gets impacted, but i'm not sure whether you want to go softer or harder.  if they are still available, try to get your hands on the old-style Modolo sinterized pads.  expensive, but i've never had problems with them.  and they offer superior stopping ability in the wet.

hope this helps.

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Permalink Reply by Mike Schwab on December 14, 2012 at 10:34pm

http://sheldonbrown.com/rim-brakes.html

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Permalink Reply by Doug Haynes on December 15, 2012 at 2:32am

It's just a fact of life, pick the chunks out.

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Permalink Reply by Far'arned Retrogrumpalunkus #63 on December 15, 2012 at 4:51am

try changing pad material/brand.

Kool stops don't do this for the most part in my experience and are both easy on your rims and stop better.  They don't last as long though but most people ride so infrequently that they never wear out pads before they get hard and old anyhow.

When I built up my current road bike I used the stock Shimano pads that came with my calipers for about 60 miles on brand new Sun CR-18 rims.  They ate into them something terrible and had the same issues you are speaking of.   I swapped out to Kool Stops (salmon in front and dual salmon/black in the rear) and the issue stopped although the damage to the rims can still be seen even now.  

This past summer I decided to swap out the rear wheel from a 32-spoke to a 36-spoke because I am a fat ass and was having issues with it.  I bought a new CR-18 rim and built a new rear wheel.   I noticed recently that this newer rear rim still looks like new without any tracking on the brake surface after almost 2000 miles with the Kool Stop pads only.   The front rim has actually gotten a little bit better over time as the Kool-stop made it smooth again without any of the rutting/grooving that was there before.  There is still a tiny bit of discoloration where the Shimano pads fooked it up that first 60 miles.  I think that is the anodizing missing in that area like David was talking about above. 

I am a fan of Kool Stop pads.  They work very well and give great feel in the wet or dry.  If I ever buy another set of Shimano brakes I'm going to toss the Shimano pads right in the garbage and go with Kool Stop from mile one. 

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Permalink Reply by Rich S on December 15, 2012 at 8:40am

I'll give the Kool Stop pads a shot once these wear out. In the meantime I'll just pick out the bits. If it keeps happening I might replace them sooner.  

Thanks for the feedback everyone!

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Permalink Reply by Far'arned Retrogrumpalunkus #63 on December 16, 2012 at 2:57pm

A little bit of Barkeeper's Friend powder on a moistened sponge works wonders on alloy rims to get that "crud" off the braking surfaces.   Whether it be balled aluminum oxide/metal-bits splooge, road schlopp, gummy melted-on brake pad residue, or any combination of these it will gently remove it all without doing any serious damage to  the alloy although if you rub long enough you will eventually take off any anodizing.  That may be necessary if the surface is really beat up to get it halfway smooth again.  

Barkeeper's Friend works well on steel rims as well and gets off a lot of the surface rust on them.  In addition to the fine abrasive power, it contains a tiny bit of oxalic acid -the same stuff that restorers use to dissolve rust gently from steel bike parts.  

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