# Shimano Rear Hydraulic Brake Squeals...



## Piper J3 (Nov 4, 2021)

I have Shimano hydraulic disc brakes on my Trek 8.5 DS bike. Front brake is perfect and rear brake has squealed/chattered since new. Now I’m trying to diagnose and fix problem. I have installed new resin pads, semi-metallic pads, scuffed rotor with 240 grit sandpaper, cleaned rotor with lacquer thinner. Rotor runs true and caliper is aligned so both pistons contact evenly.

If I run rear wheel at high speed on a bike stand, the rear brake works great. When I lower the bike to the ground, and push it forward (with no rider) and apply rear brake - it squeals. Push bike backwards, apply rear brake, and no squeal.

I have looked at YouTube videos and searched internet to find solution with no avail.

Any help is appreciated…


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## duriel (Oct 10, 2013)

Pain, might try taking the rotor off and cleaning the mount, reinstall.


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## tlg (May 11, 2011)

Piper J3 said:


> When I lower the bike to the ground, and push it forward (with no rider) and apply rear brake - it squeals. Push bike backwards, apply rear brake, and no squeal.


Does it squeal when you brake while riding?

My brakes do this when I stand and push/brake. But not when I brake while riding.


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## PBL450 (Apr 12, 2014)

It’s new. Bring it back to the dealer, send it back to the seller… The hell I’d be chasing any fix on a brand new bike or anything else. It’s broken. 


Sent from my iPhone using Tapatalk


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## shrubs (Apr 6, 2021)

You have done some great things to fix the squeal. You might be in a “only this brake system” situational. Stop spending money and using time and start contacting someone who will give u a replacement assembly. Warranty or not.


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## aclinjury (Sep 12, 2011)

in the mbt world, if everyone is trying to fix their brake squeals, then nobody would be on the trails. Just ride the damn thing, the squeal will go away eventually. That's what I did on my mtb, time and again.


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## J.R. (Sep 14, 2009)

If you're using new pads and a freshly cleaned rotor you may find it helpful to "bed" the pads in. 

Something like this. How to bed new disc brake pads


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## 202cycle (Sep 13, 2011)

Remove the pads and check the back of them for a very faint ring of mineral oil. I have seen numbers of Shimano brakes with a very slight leak from the piston. You just can't get the squeal to go away. Shimano has warrantied every one of them.


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