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Discussion Starter · #1 ·
I have old Shimano M395 disc brakes, slowly learning how to service them. I did a bleed and completely replaced the fluid and sanded the pads, now my back wheel has a rattling sound when it spins at high speed, when I remove the pads and spin the wheel the sound is gone so I am confident the sound is from the rotor hitting the pad. The rotor has a VERY slight warp in it, probably 0.5mm or less. I don't think I can bend it back without just making that worse, I can't even accurately see where the warp is its just barely noticeable while the rotor is spinning.

I'm wondering if I could have added too much fluid and the pistons are sticking out too far, I used the spacer that came with the bleed kit, but it kept falling out so I may have made mistake.

Going to check the pistons and try this method here to see if I can fix it:


Looking for any other suggestions for what I should try or look out for.
 

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Discussion Starter · #7 ·
How did you bleed/replace the brake fluid?

Did you use the proper bleed blocks?

When you pushed the pistons back into place, was it smooth or difficult?
Mostly just tried to follow GMBN videos. Removed the pads, pushed the pistons in (I think this was smooth), inserted the bleed block, connected the funnel to the lever and pumped fluid through the caliper. It seems like if the block was too small and allowed the pistons to push out to far it could cause this? I used the block from the shimano bleed zone kite, as far as I know it is correct, maybe not.

Also for what it's worth, I've probably had this problem for awhile, back brake used to squeal sometimes even when I wasn't pulling the lever, now it's just more of a jingle because the pads are sanded and not squealing. Not sure why I didn't think about this until today! I was expecting to find the rotor was bent and causing this, but after taking stuff apart and having a closer look that's not really the case. I've been unhappy with the brakes on this bike for awhile, had them serviced at my LBS once but I think all they did was replace the pads.

Burnt out and a few beers in tonight, going to go through it all again tomorrow and see if I can figure it out.
 

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You say "rattling sound", that makes me think it is not disk rubbing against the pads, but something else. Do you hear the sound when riding, or when bike is on stand? My Deore brakes did rattle a little, that was just loose pads, spring and pin, nothing to worry, they are supposed to be to some degree. Try lifting the bike off the ground a little and dropping it - do you hear the rattle?
The way you describe the bleed, you've done it right, the bleed should not be a reason for the rattle, unless you've forgotten to tighten something, or the caliper was encrusted with mud and now you've cleaned it, so the pin rattles :)
The important thing is - do the brakes work, does the lever feels firmer than before, does the wheel rotates long enough time before stopping (when on stand)?
 

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Discussion Starter · #9 ·
You say "rattling sound", that makes me think it is not disk rubbing against the pads, but something else. Do you hear the sound when riding, or when bike is on stand? My Deore brakes did rattle a little, that was just loose pads, spring and pin, nothing to worry, they are supposed to be to some degree. Try lifting the bike off the ground a little and dropping it - do you hear the rattle?
The way you describe the bleed, you've done it right, the bleed should not be a reason for the rattle, unless you've forgotten to tighten something, or the caliper was encrusted with mud and now you've cleaned it, so the pin rattles :)
The important thing is - do the brakes work, does the lever feels firmer than before, does the wheel rotates long enough time before stopping (when on stand)?
Hard to describe the sound, but it sounds like the rotor is hitting the pad and rattlling/ringing. Maybe also loose pads, but I'd rather not have the rotor contacting the pads while riding without pulling the lever. I've tested with and without pads installed, without pads there is no noise and with pads there's the noise and a noticeable friction with the wheel slowing down a little faster than it should. Ultimately the brakes work and feel better than before (which is not saying much lol). Only reason I suspected the bleed is if it was possible to have too much fluid and have the pistons sticking out too far in an idle state. I think I'm going to just get new pads, clean and check everything. My pads are old and often have had problems with squealing.
 

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Discussion Starter · #12 ·
Just to follow up with this, I got new brake pads and fixed this with the business card trick in the article I linked with in the OP. I don't think my old pads were causing the noise but they were squealing a lot so I wanted some new ones. When I installed the pads I adjusted the caliper with the business card inserted and it's completely silent, went for a ride yesterday and it was really nice to have a mostly quiet bike again.
 
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