Hi Chaps,
While bleeding some XT 775 brakes this evening I noticed little air bubbles around the inside of the piston... is this is dodgy seal? Or is it just air escaping normally from behind the piston?
I'm guessing being shimano if it's a dodgy seal, then it's a new caliper body.
Thanks
Ricks
Just had the same issue. New caliper time I'm afraid. Sent the caliper back to Merlin and they agreed it was goosed. They've returned it to Madison but Madison haven't got any M775 calipers left so ended up having to buy one off Hargroves Cycles online and I'll hopefully get some credit off Madison via Merlin.
New brake feels lovely and positive now though, which is just about the only consolation 🙁
I had this recently, but it was on a Hope M4. It was indeed the seal gone.
(Off to Hope and fully refurbished with new pads for £15).
Rob - how quickly did the brake deteriorate after a bleed? i.e. will the lever last a few rides before enough air has leaked into the system?
Rubbish though, as I've just replaced the lever on this brake due to dodgy master cylinder seal - must have got contaminated somehow as they're just over a year old.
Had exactly the same problem with an M765 rear caliper. Took me ages to diagnose the problem. Ended up replacing the hose, then the lever before I finally noticed the bubbles around the piston.
It was obviously gone before the bubbles were noticable as I couldnt seem to get any power out of it, even after a fresh bleed.
Rick - mine kept feeling as if it constantly needed bleeding for a few months until I noticed it, but the clincher for me was that I got some fluid through the seal at one point which got on the pads and obviously severely affected the brake. I only did one ride with it like that then sent the system back to Merlin
Cheers Rob, it's only bubbles at the moment - so I'm hoping the seals will hold out - I wonder if you could replace the seals with something of the right size
Not aware of any replacement seals out there for Shimano stuff unfortunately. Once its bubbling the caliper is useless. Bin and replace.
Oh well, thought I was being clever only buying a lever replacement - turns out I wasn't 😕
If its any consolation i did the same!
It's some consolation, I would just buy some new XTR calipers - but that'd mean dumping my older Shimano pads, buying a new hose kit....