Shimano Deore XT M775 Brakes only work well when it wet. Why?

pus2meong · Nov 29, 2020

So I have this Deore XT M775 brake set. When I put it on my bike, the braking performance is so poor. The brake pads is like pinching a slippery rotor.

I already clean the rotor and also sanding the brake pads, still nothing. And now, it even howling if I yank the lever too hard. There are no problem with my rotor, since I use Deore XT M8000 brake set, it perform amazing.

However, when I pour some water on the rotor and on the M775 brake caliper. Suddenly it can brake very well.

Is anyone know why?

I could just buy a new brake pads, but still... kinda curious about this too.

Pisgah · Nov 29, 2020

I used those brakes for a long time without problems. Try swapping pads. Make sure your rotor size is correct.

Boozzz · Nov 29, 2020

I've had this before. When cold from the shed, it's crap. When you throw water on, it's good. When they heat up, it's crap again. With me it were slightly contaminated pads/disc rotor (with water on the rotor, you could see a slightly oily looking film inside the holes of the rotor, like blowing bubbles). Thoroughly cleaning the rotor again and throwing on some new pads was the fix. Tried salvaging the old pads by frying them on top of a gas stove, but they weren't great after that.

Jayem · Nov 29, 2020

Those brakes are known to leak/weep at the caliper piston seals. Happens when they sit for a few weeks without being used.

Simvtt · Sep 27, 2022

I'm having the exact same issue here. Cleaned the rotor, replace the pads, nothing works. However when I pour water on the caliper, it works great again ! Have you found a solution ?

Shimano Deore XT M775 Brakes only work well when it wet. Why?

pus2meong

Pisgah

Boozzz

Jayem

Simvtt

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