I recently purchased a bike that clearly needed fixing, for a great price. I've given the bike a bit of a tune-up, but one thing that won't seem to go away is the squealing sound coming from the disc brakes. The brake pads look fine, but I went ahead and cleaned them with isopropyl alcohol and shaved them a little with light sandpaper. I also cleaned the disc with the same alcohol, but the sound is still there. The disc itself appears to be straight. Any other thoughts?

  • 1
    Maybe axel is out of shape or flex? Guessing you’ve already checked calliper alignment? Is it a constant noise or particular place in the wheel rotation?
    – Hursey
    Oct 13, 2022 at 18:19
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    Hmmm, not sure I fully understand your comment @Hursey. If you are going down a hill, you will need to put your brake on partially to slow down or am I not fully getting your comment...?
    – Brannon
    Oct 13, 2022 at 20:33
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    @Hursey Any decent disc brake can absolutely be half-on, in fact it's one of the advantages of discs that you can modulate any braking strength under any condition. Now, that doesn't mean it's a good idea to gently drag the brakes on an entire descent – this can overheat the brakes; releasing them when possible in exchange for harder, shorter braking is generally better than continuously braking at low strength. But this only starts to matter if you drop at least 100 m, or more, depending on the brake type – big 4-piston brakes are hard to overheat if you don't deliberately maximize heating. Oct 13, 2022 at 22:25
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    @Hursey As leftaroundabout said, being able to control your braking with very good precision is one mark of a good rider. The idea of "brakes only on or off" is more of a macroscopic view to ride faster (you should wait to brake as late as possible). However, when braking, you most definitely need to be able to control braking power.
    – MaplePanda
    Oct 13, 2022 at 22:39
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    Does this answer your question? Front disk brake squealing and many others. please use search and peruse the most likely questions answers.
    – mattnz
    Oct 14, 2022 at 2:45


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