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After replacing my worn-out Magura brake pads (MT4 brakes, 7P brake pads), I now have a continous light friction noise when the wheel is spinning (front wheel).

The brake disc is brand new as well. The former one was slightly bent by a couple mm. I noticed the pistons are not fully back in their original positions.

I've tried to fix that by pushing the pistons back in their original position, removing a few drops of brake oil, tried also applying Magura's instructions to "re-mobilize" the pistons, all to no avail: the issue keeps on coming back as soon as I hit the brake lever. The friction noise is back with the piston again not returning to their original positions.

I am totally clueless regarding further steps to resolve the noise and piston return issues. Any advise would be very welcome.

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    From what you've written it's not clear that you've adjusted the caliper to equalize the pad gap - is it rubbing in spite of all efforts to do so? Nov 2, 2022 at 19:59
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    If the wheel spins freely, they should also stop rubbing after the pads have worn in a little -- one long descent is usually enough. A light noise with no effect on spin isn't really a problem.
    – Noise
    Nov 2, 2022 at 20:23
  • Sorry, indeed I didn't mention that part - yes I tried adjusting the caliper, the space between the pads and the disc remains too narrow given the piston's positons so there is no optimal caliper positionning. @NathanKnutson , thanks - when pushing the pistons back, I could then align the caliper properly. Only that, as soon as I hit the brake, the pistons would again stay in a position where they are too taking too much space resulting in the pads being too close to the disc.
    – Nicolas
    Nov 2, 2022 at 20:25
  • @Noise - thanks, the wheel does spin freely, I am not feeling this is making the bike dangerous to ride in anyway, just concerned it will worn the pads quicker and I am also a bit frustrated by those pistons which won't get fully back into their original positions (which I feel could help prevent wearing out those pads).
    – Nicolas
    Nov 2, 2022 at 20:30

1 Answer 1

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From where you're at now, this is what I would do:

  1. Take out the wheel and pads.
  2. Intentionally overextend the pistons with the lever. Clean them and the whole caliper thoroughly with alcohol.
  3. Swab Royal Blood onto the clean pistons, then push them back in. Repeat several times until they seem to be moving as freely as they're going to.
  4. Put in a bleed block (I always use a 10mm allen t-handle for Magura because it's way stiffer than the official yellow plastic one and is the same dimension. The stiffness is good because the way the official ones compress when you test at the lever after the bleed can make troubleshooting difficult). Bleed the brake.
  5. If uneven retraction issues continue, live with it or replace the caliper.

Also, having the mounts properly faced will only help reduce these issues, even if it was good enough when the caliper was new and working perfectly.

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    Thanks for the suggestion, I'll give that a try tomorrow morning and share the results.
    – Nicolas
    Nov 2, 2022 at 21:05
  • I'v followed your steps above, I could see the pistons move freely and completed the bleeding process. The friction issue is still there but one major update: the disc is not continously in contact with the pads, which makes me think the caliper is not at fault but this is rather an alignment issue between the caliper and the wheel. Anyway, the contact point is so slim, looks like it way less than a millimeter, I will leave it be and wait for the pad that has the contact point to wear out a little. Thanks for you advices
    – Nicolas
    Nov 3, 2022 at 10:24
  • @Nicolas Maguras have really, really tight pad clearances. If you haven't already, try aligning the caliper by hand for extra precision.
    – MaplePanda
    Nov 3, 2022 at 14:11

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