gnrboyd

My rim brake shoes were getting worn so I replaced them recently. Prior to replacing them, my front rim had been making a scraping sound when braking while my back was fine. (The sound is similar to lightly sanding wood with sand paper.) I replaced them thinking that would solve the issue, but it did not. My previous pads were some off brand but I replaced them with Shimano M70T3 pads. I even cleaned the rims with alcohol and even lightly with a fine scotch brite pad. They look much cleaner but it didn't affect the scraping sound. Other than trying to find another type of pad, is there something else I could try? (Yes, they are installed and adjusted correctly.)

Thanks for your input.

veganbikes

Did you check to make sure it is not an errant cable or something else scrapping? I have had that happen more than once. Sometimes the sound you think you are hearing is not the sound at all.

Also useful tip, get brake shoes with really high quality pads, having actual metal shoes with replaceable pads means better braking and more savings in the long term as you are just buying pads. It is a cheap upgrade that can make a big difference.

gnrboyd

I disengaged the cable and just pushed the pads to the rim so I don’t think it could be anything else. The back wheel is fine so it doesn’t make sense that it would be pad quality. I’m stumped.

Andrew R Stewart 

So no noise when the pads/brake are away from the rim and noise only when the pads contact the rim? No cable end scraping against the tire?

What's the surface condition of the rim? Any scoring or evidence of something scratching the brake track? If so then most likely the old pads had bits of grit in them and were scraping the rim at those points. Fresh pads solve the cause but now the rim might need light sanding along the brake track to "soften/smooth down" the gauged/scraped remaining surface. The rough surface, especially with a hard compound pad (try digging your fingernail into your new pads and then compare to others), can cause a sanding type of noise. Andy

reburns

Some Shimano pads are very abrasive. They can be loud and also hard on rims. I would switch to a different pad. I’ve had really good luck with Swisstop green pads. Quiet, easy on rims, do not pick up embedded grit, lots of stopping power in wet or dry conditions, and last forever.

gnrboyd

Nothing scraping the rim other than the pad. I see lines on the rim but nothing that appears to be a grove or scoring at least by running your finger over it. I have periodically picked out flakes of metal from the pads but from what I understand, that is normal. See photo of rim.


I will have to look for those pads. I assume they make them for V-Brakes? My V-Brakes are what came with the bike in 2014 and don't appear to be a very high quality. I have close to 12K on the bike so it might be time for an upgrade at some point.

randallr

Oh, nice, you have a wear groove to let you know if you've worn out too much of the rim.
I scrub my brake pads with a toothbrush to get any grit out of them when I wash the bike.

gnrboyd

I ride a gravel trail mostly and after almost every ride, I wipe down the rim with some simple green to get most of the dust off. I sometimes will also clean it with alcohol. The back rim has the same brake pads and doesn't make the noise. I'm baffled.

freeranger

Surprised that both aren't making the scraping sound if same pads front and rear. Not familiar with Swisstop pads, but years ago I switched over to Kool-Stop Salmon pads and they are all I will use now. Way back when I had some Shimano pads that I could actually pry what appeared to be metal shards out of. Switched to the Kool Stop and haven't had a problem since.

ChrisAlbertson

I just had the exact same problem with the Shimano pads. The noise sounded as if there was a stone wedged into the groves in the brake pad. Then I took the pad off and looked. It seems that Shimano puts a metal wire inside the rubber so that if the rubber is worn the wire is exposed and makes a really horrible noise. I had two pads where I can see the exposed wire in each. I don't know where else this metal wire would come from if not the factory The front pads wear faster and the noise is worse. It means it is time for new pads. I just yesterday got four new pads via Amazon "one-day" shipping and the problem is solved.

I know they place metallic wear indicators on automotive disk brake pads so they will make a bad noise before they completely wear out but I never heard of this in bike brakes. I'll post a photo later an maybe cut up the old pads to see what is inside.

In my case this was on an MTB I am overhauling and these were 70-millimeter v-brake pads.

Greg C.

I installed new Giant brand pads on my older Schwinn hybrid. The pads squealed from the start even after fine tuning. What worked to stop the squeal was cleaning the rims with alcohol then cleaning/coating the pads with an auto rubber protector that I had. The stuff is called "gummi pflege". Some of the brake grab was gone at first but after using them a little they worked fine.

gnrboyd

Update: After another round of cleaning the rims, nothing changed. The front still sounded like radio static. The rear sounded fine.

I then put my old (very worn & not high end) front brakes back on and the sound was normal (quiet) again and they had much more gripping power. I left the new brake pads on the back.

I then went for a ride. Not too far into the ride, I realized the back was also making the same grinding noise. I guess having weight on it made a difference.

Conclusion: These Shimano M70T3 pads are junk. Perhaps a manufacturing defect during the production run or these shoes are just junk to begin with. Not sure. Regardless, I won't be buying these again.

Jean_TX

I used to have some rims (Mavic CXP22) like that on my bike. I also used to hear a scraping noise when braking, like the brakes were sanding the rims. I closely looked at the pads for any embedded material and found nothing. But I did notice that the pads had been ground down to correspond with the surface of the rim - they had a protruding ridge that fit into the wear groove. I think the scraping noise was due to the rim abrading the pads and not the pads abrading the rim. My solution was to get new wheels.

gnrboyd

That's an interesting observation on your brake pads/wheels. I take it the new rims don't have the groove?

I had a similar problem with the grove cutting into the pads a little bit and creating an uneven surface with the original pads (Tektro) that came with the bike. I didn't have that issue with the replacement pads (Off brand) I put on a couple of years ago. Neither of them made the scraping noise the Shimano pads are making. I think they are just too hard.