Good evening,

having some trouble with the g/f’s XT brake (M765). It behaves like a little oil is getting onto the pad – solid lever feel, works well in wet/muddy conditions, but when it dries up it always (quickly) loses bite. Currently you can just about get the wheel locked up with 2 fingers on the lever and weight forward, but last weekend in the mud at Inners it was absolutely sorted

It’s been bled a LOT, hose has been replaced as it was looking worn, rotor replaced, several sets of pads, but I simply cannot get to the bottom of what’s going on! No signs of any oil coming out of the pistons and i’ve done the “fasten the lever to the bar trick” to make sure there can’t be any air in the system.

I was going to just get a new caliper off Ribble’s for £32 but they’re now sold out 🙁

Is there anything I could be missing here? Just to make things more tricky, heading to France at the end of the week so could really do with getting it sorted.

Cheers,
Mark

I posted this elsewhere in answer to a similar / same question. Particularily relevant if she used them in the cold – ime.

Sorry for being lazy:

It could be something else (but leaking caliper seals is a common problem ime with recent Shimano calipers).

To check – take the wheel out , pads out and jam somthing plastic between the pistons (a tyre lever works well). Then pull the lever till you get a real firm clamp. You will probably see fluid / bubbles from around one of the pistons.

Also check for any signs of oil on or near the calipers / mounts etc. Even a tiny amount is the start of real trouble.

How old are they – under warranty (12 months)?

I think for mine its something to do with using them in extreme cold – my winter bike suffers way worse.

If the piston seal is your problem (it could be something else!):

I’ve tried finding the seals on their own (the bit that seems to cause the leak) but cant be got. The good news is that you can buy a new SLX caliper for £25 from CRC which works fine (even with servowave levers).

Also a Deore caliper will work too a save a few bob. Installing and bleeding is easy, but you will loose about 1/2 inch of the hose (’cause you cant reuse the insert/olive)