Got some issues with my M785 brakes.
Few weeks ago after a ride the front brake just locked on.
I cleaned the bike off and wheeled it to the garage and by the time I got there it had sorted itself.
It’s been fine until last night when I noticed the pistons seemed to be stuck out and not returning.
I removed the pads and pushed the pistons back in with a 10mm spanner.
Put the pads back in but now the lever goes al the way to bar before biting the rotor and the lever doesn’t spring back.
Any suggestions for a cure? Bleed it? Send it back under warranty?

I have a theory… could you check the part of the lever that acuates the roller on the end of the piston shaft. (tricky to describe… push the lever forward so it disengages and see if the profiled ‘cam’ area is worn)

My SLX rear doesn’t return properly and it seems to be that the cam area is worn in a similar manner to a hooked chainring, so it grabs the piston and doesn’t fully let go~ I haven’t experienced the locked caliper, but wonder if it is what happens over time.

Is it doing what mine was doing near the end of this clip?

[video]http://m.youtube.com/watch?v=yBFzIehsmqA[/video]

I sent it back and it was replaced under warranty. Never did find out the cause exactly..

Don’t push the pistons back with a metal object or the ceramic pistons will crack.
I’d have a check especailly as your lever is now going back to the bar.

Thanks for the pointers, I will take a closer look when I get home!

Warranty job, I’m on my 3rd pair of XTR trail brakes. They only last about a year then the lever goes to bars and fails to return, you also get a problem with the pistons that no matter how many times you pump the lever they will not pump out.

I feel that they have a issue with the master cylinder/lever assembly but never get an answer as to what happened when I get them warranted. Like I said I’m on my 3rd pair in under 2 years, good thing that XTR have a 3 year warranty. I think XT has a 2 year warranty, if I could afford it I would change to something else which is a real shame as they are great brakes when they are working.

Thanks Stu,
I’m going to get them looked at under warranty as they are less than 12 months old.
They have been trouble free up until now. Still way better than the Elixirs they replaced!

Shimano brakes issue shocker. Can’t wait to see what the resident Hope Haters will have to say about their brake of choice failing. 😛
If all else fails you could always try and call Shimano direct and see if their customer service equals That of Hope.