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After 30 years I put my old road bike into semi-retirement and have been riding a new Specialized Sequoia for about 2 weeks. It’s the first bike I’ve ever had with textured braking surfaces (Alex AT400 rims), and the brake shoes have been collecting metal fragments which make a horrible hissing noise whenever the brakes are applied- a construction worker near a running bulldozer actually commented on how loud they were. If I pull the shoes and pop out the metal with a pin they get nice and quiet, but after just a couple of miles they start to get noisy again. The brakes appear to be correctly adjusted. The rims have no obvious visual or tactile defects. It affects both rims, all four shoes, whichever brake is used more (front or back), its shoes collect the most fragments.

Is this the nature of the beast? Is it a break-in issue? Is there something wrong with the shoes or rims? Would changing shoes help?
 

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Like Spunout says, replace the brake pads. Many Shimano OEM brake pads are known to collect slivers of aluminum (which reduces braking power, wears out rims, and squeels), so use a quality aftermarket pad like Kool Stops instead.
 

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Cat 6 rider
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Discussion Starter #4
Mark McM said:
Like Spunout says, replace the brake pads. Many Shimano OEM brake pads are known to collect slivers of aluminum (which reduces braking power, wears out rims, and squeels), so use a quality aftermarket pad like Kool Stops instead.
Mark (and Spunout);

Thanks for the information. I'll try changing the pads and see if that helps.


L33
 

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I have had this same problem with new rims with the machined breaking surface.
It is worse on rims with a rough ribbed looking surface.I think the ribbing causes metal to flake off on a new rim and eventually the problem subsides.I am not sure you can blame the pads because I have not had as severe a problem with rims with smooth braking surfaces.In any event you must dig the metal bits out of the pads or you will ruin the rim.I had this problem with a new Mavic Cross Ride MTB wheel and it nearly ruined my all day ride because I had to stop and clean the pads about five times.
 

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Cat 6 rider
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Discussion Starter #6
jordan said:
I have had this same problem with new rims with the machined breaking surface.
It is worse on rims with a rough ribbed looking surface.I think the ribbing causes metal to flake off on a new rim and eventually the problem subsides.I am not sure you can blame the pads because I have not had as severe a problem with rims with smooth braking surfaces.In any event you must dig the metal bits out of the pads or you will ruin the rim.I had this problem with a new Mavic Cross Ride MTB wheel and it nearly ruined my all day ride because I had to stop and clean the pads about five times.
I've never had a problem with rims with smooth brake surfaces, ever (one of the reasons I asked- I've also never had alloy rims before. I'm still only getting one ride between cleanings, but it doesn't seem to get as bad as fast as it was. I'll still probably change the brake shoes soon (as soon as I find a local shop with Kool Stop pads) because the originals are getting fairly beat up with all the metal removal.

Of course, that brings up the question, what is the purpose of the ribbing on the rims? Aerodynamics, like the dimpling of a golf ball? Better wet stopping power, because dry they actually seems a bit worse than smooth rims?

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No ribs

California L33 said:
Of course, that brings up the question, what is the purpose of the ribbing on the rims?
Ribbing on the rim sidewall is actually quite rare. What rims are you using? As far as I am aware, none of the quality modern clincher rims have this "feature." I suspect it was meant to improve wet weather braking, through there is no evidence that this works. If you've never used alloy rims before, what were you using?
 

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Kerry Irons said:
Ribbing on the rim sidewall is actually quite rare. What rims are you using? As far as I am aware, none of the quality modern clincher rims have this "feature." I suspect it was meant to improve wet weather braking, through there is no evidence that this works. If you've never used alloy rims before, what were you using?
The ribbing I referred to is seen as coarse machinig marks on the braking surface.Some rims have a very smooth machined surface and many now have a coarser "ribbed" appearance and these coarsely machined rims seem to flake off metal when new.It is most noticeable on cheaper Taiwanese rims such as Alex,but I also had the same problem with a Mavic Crossride wheel.I suspect the coarse machining has no purpose other than being a less expensive method of manufacture.
 

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Ribbing = grooves?

Kerry Irons said:
Ribbing on the rim sidewall is actually quite rare. What rims are you using? As far as I am aware, none of the quality modern clincher rims have this "feature." I suspect it was meant to improve wet weather braking, through there is no evidence that this works. If you've never used alloy rims before, what were you using?
I think the original poster might be referring to the machining grooves on machined sidewalls. Although manufacturers could probably leave a smoother machined surface by using different cutting tools or speeds, they apparantly choose to leave relatively deep machining grooves.

Personally, I think the purpose of these grooves is to reduce brake squeeling during test rides on new bikes (brake pads on new bikes are not likely to be worn in and may not be perfectly adjusted, and therefore may be more prone to squeeling). After some initial use, these grooves disappear as the rim gets worn smooth. The wearing down of these grooves does not degrade braking performance, and may actually improve it.
 

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Discussion Starter #10
Kerry Irons said:
Ribbing on the rim sidewall is actually quite rare. What rims are you using? As far as I am aware, none of the quality modern clincher rims have this "feature." I suspect it was meant to improve wet weather braking, through there is no evidence that this works. If you've never used alloy rims before, what were you using?
What material were my rims if they weren't an alloy? Cast iron. OK, you got me on a technicality. I guess steel is an alloy. I should have said light weight alloy.

The current rims I was asking about are Alex AT 400.

And maybe you got me again. The "ribbing" we've been talking about are extremely fine groves cut in, and running around the outside of, the rim on the braking surface. I've attached an image with considerably enhanced contrast which makes them look far deeper than they are. Without the enchanced contrast it's quite hard to see, though it can be felt. (The center groove with the white highlight is Alex's wear depth indicator.)

L33
 

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Terminology

First, us old timers use the term "alloy" to refer to aluminum. However, if you really have been riding chrome steel rims, then all I can say is WOW. I haven't had rims like that since I bought a used Schwinn 3 speed for commuting, back in 1974. The braking was SOOOO bad in the wet that I replaced the rims as soon as I could.

At any rate, the picture you show is not likely of a "ribbed" rim. What you are seeing there is most likely caused by contaminants in the brake pads scoring the rim during braking. IOW, your braking action caused the grooves - the grooves did not come from the factory. Your chicken and your egg are reversed - it is the metal spalling off the rim or grit you picked up from the road that has grooved your rims, not the grooves that are causing the metal fragments to come off the rim.
 

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Kerry Irons said:
First, us old timers use the term "alloy" to refer to aluminum. However, if you really have been riding chrome steel rims, then all I can say is WOW. I haven't had rims like that since I bought a used Schwinn 3 speed for commuting, back in 1974. The braking was SOOOO bad in the wet that I replaced the rims as soon as I could.

At any rate, the picture you show is not likely of a "ribbed" rim. What you are seeing there is most likely caused by contaminants in the brake pads scoring the rim during braking. IOW, your braking action caused the grooves - the grooves did not come from the factory. Your chicken and your egg are reversed - it is the metal spalling off the rim or grit you picked up from the road that has grooved your rims, not the grooves that are causing the metal fragments to come off the rim.
Re-read the posts,then go to a bike shop and examine new machined rims and you will find grooves in the braking surface of variable coarseness.Look at the Alex rims on inexpensive bikes 350-800$ and you will find the grooves.None of the posters are imagining the grooves or having problems with thought process.Obviously if you ride the bike with the metal bits in the pads you create new, more severe grooving from the metal to metal scoring.
 

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Discussion Starter #13
jordan said:
Re-read the posts,then go to a bike shop and examine new machined rims and you will find grooves in the braking surface of variable coarseness.Look at the Alex rims on inexpensive bikes 350-800$ and you will find the grooves.None of the posters are imagining the grooves or having problems with thought process.Obviously if you ride the bike with the metal bits in the pads you create new, more severe grooving from the metal to metal scoring.

You don't have to go the bike shop. Specialized's own web site lists them as "machined sidewalls." It might be as simple as that it's cheaper to grove them than polish them.

Anyway, I wanted to tell everybody I changed the brake pads as suggested. I put standard black Kool-Stop pads on. The difference has been utterly amazing :D In the 75+ miles since I've put them on I've had not one, _not one_, metal shard in a brake pad. I was actually avoiding routes with sharp turns and stop signs, and doing a lot of slow, easy decelerations. Since then I've been able to treat it like a normal bike- just squeeze the brakes when you want to slow down- how novel. The difference has been so dramatic, and it was such an easy fix, that I'm probably going to send the pads to Specialized. I can't imagine they want their bikes, even their "price point" bikes, needing service after every single ride- especially over something as cheap as a brake pad. As for which pads were causing the problem, I don't know who made them. They're unmarked.
 

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Building on this, is there an effective way to remove the dark pad residue from my rims? I'm currently riding on Shimano R550s, and though they're only a few months old, it seems that the scoring has been packed with brake dust and/or residue that I can't remove with soap and water. I'd like to avoid using acetone or anything that harsh. Do these dark streaks and scores permanently affect braking, or would I be alright if I just got some Kool-Stops and carried on normally?
 

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Discussion Starter #15
MaestroXC said:
Building on this, is there an effective way to remove the dark pad residue from my rims? I'm currently riding on Shimano R550s, and though they're only a few months old, it seems that the scoring has been packed with brake dust and/or residue that I can't remove with soap and water. I'd like to avoid using acetone or anything that harsh. Do these dark streaks and scores permanently affect braking, or would I be alright if I just got some Kool-Stops and carried on normally?
I have used rubbing alcohol with no problems, though I'd avoid soaking the rubber tires with it. On the other hand, I've also cleaned them when washing the bike- a cap full of dishwashing soap (not detergent) mixed in a bucket of water, applied with a soft towel, then rinsed with water.

I'm not sure why soap and water haven't worked with yours. Have you tried an old toothbrush to make sure you're getting into the grooves?
 
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