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Today I braked my bicycle from 50 km/h with my front rim brake and heard a really nasty sound coming from the braking surface of the wheel, and I saw some metal shavings as well. The brake has been randomly making these noises for a little while, but this is the first time I've seen shavings. The brake pads and rims are about two months old.

Do you think my wheel is toasted or my brake pads are too hard?

I have rim brakes. It has been happening for a while, randomly but just the sound, never seen the metal shavings flying from my rim. And yeah, the brake shoes are like 2 months old, as well as the rim.

The rim is aluminium.

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  • What are your rims made of? I don't think you can get a spark off aluminium so I suspect they're steel. In that case you might need to choose your pads carefully as steel rims are less effective for braking and fussier about pad material
    – Chris H
    Commented Mar 17, 2019 at 16:07
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    I'm guessing the pads were poor quality and have disintegrated, or they were improperly installed.
    – Daniel R Hicks
    Commented Mar 17, 2019 at 17:59
  • @FlorinOprea aside - I've edited this info into your question, so its not a long forum-like list of changes. You can do this too using the Edit link.
    – Criggie ♦
    Commented Mar 17, 2019 at 19:15
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    Photos of rims and pads would help remove a lot of guess work as to where the problem lies.
    – mattnz
    Commented Mar 17, 2019 at 22:01
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    @FlorinOprea It would be better to edit the photos into your original question. This site is a Question & Answer site; we don't do long discussion threads. Answers are for... well, answering the question.
    – anaximander
    Commented Mar 18, 2019 at 14:39

3 Answers 3

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Sparks coming from rim brakes sounds like there's some hard object, such as a piece of grit or metal, embedded in your brake blocks. After two months, they shouldn't be badly worn, unless they're very soft, but pads will eventually wear enough that the metal cartridge mount is now touching the brake track.

You should check your rim for damage. If it looks badly scratched up, it might be damaged. Also, hold a steel ruler or other straight edge radially against the rim. A new rim should be almost straight; worn rims develop a concave profile as braking erodes the material. (By the way, if there's one perfect groove right around the rim on both sides, which looks like it was cut by a machine, that's a wear indicator: as long as you can clearly see that groove, the rim's not overly worn, assuming it's in good general condition.)

My guess would be that the sparks were from something getting lodged in the brake pad and the noise before that was due to poor adjustment. Brake pads need to be "toed in" slightly so that the front end of each pad touches the rim slightly before the rear end. If the rear end touches first, the brakes judder and vibrate.

If you're not confident that you can diagnose this problem yourself after getting help here, you should get the bike checked out by a bike shop. The front brake and front wheel are critical to your safety.

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    "If you're not confident that you can diagnose this problem yourself after getting help here, you should get the bike checked out by a bike shop." Big time. I got a concussion as a result of fixing the front brakes on my bike as a kid. (Also, pro tip: Wear a helmet.)
    – T.J. Crowder
    Commented Mar 18, 2019 at 9:58
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Some rim brake pads pick up and embed into themselves small pieces of rock and metal shavings from the rims. It sounds like you have one of these. A temporary solution is to remove the pads, dig out largest pieces and sand the braking surface until it is clean. The problem will repeat soon.

A more durable solution is to switch to a different brand. I have had good luck with Kool Stop salmons and the cheapest Jagwire from local sports store. There are probably many more good brands.

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This sounds like you're braking quite a lot (maybe too much and rather brutally) and that the metal part of the brake-shoe that holds the brake-rubber makes contact with the rim. Replace the pads at once!

It could also be that the rubber is way too soft and uses up very quickly because 2-months-old pads should not be down that much. But that depends on the type of bike which you don't tell. A BMX used for doing tricks might use brake-pads quicker than a road-bike used for racing.

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  • For the first pads on a new bike, I think 2 months is pretty normal. Many of them have cheap pads (even if the brakes themselves are good) that wear out really fast.
    – Nobody
    Commented Mar 17, 2019 at 20:11
  • @Nobody : This may be true with printers where the first cartridges are only half-full but brakepads are a safety item and I doubt that serious companies would install low quality pads on new bikes.
    – Carel
    Commented Mar 19, 2019 at 8:45

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