Xtr m975 brake issue - sticky piston help?

[ishaw]

I bought a used set of these brakes from this forum and have been waiting for the day I'd get time to fit them. Today was that day.

Started off well, the brakes were set up the 'wrong way round' so started with the front, swapped the hose, bled, fitted, all good.

Set about the rear, fitted a new longer hose, bled, fitted, not so good. When the brakes are pulled, the callipers don't fully return so rub the disc.

Some online research later, I've pumped the brakes to release the pistons (not fully) and they appear to be scored. Does this mean they are toast or is there anything that can be done to salvage them?

Gutted as now they're all fitted to the bike there's no turning back and was planning on using it tomorrow.

 

[greencat]

Re:

Have you tried cleaning the pistons? - and perhaps swipe them with a tiny bit of lube (obviously wipe off any excess before installing the pads).

Couple of hope videos might be helpful too (obviously will vary for Shimano):

[youtube]https://www.youtube.com/watch?v=akIWGqEE0PY[/youtube]

[youtube]https://www.youtube.com/watch?v=v83YFGi5uT0[/youtube]

 

[ishaw]

I've tried a little i.e. With the pads removed pulled the lever a few times to expose the piston as much as I dare, cleaned what was visible and lubed. This was how I noticed the scoring.

They don't leak though, so that's a bonus I guess but one piston is still sticky. I've managed to get them to a point where there's an even gap either side of the disc, but it's so small there's little lever movement before the brakes are on. New pads in there so I could switch to the old ones for more room but suspect it would only be a few brake cycles before things would be back as they are now.

Cheers for the videos though!

 

[02gf74]

You need to pop thr pistond out and ckean then as well as the area around the seals. Cable tie round one piston and pump lever a few times, do it in a bowl where you can catch the fluid and possibly re use it if clean.

 

[ishaw]

Sadly this made it worse, it now leaks as I think the dirt was plugging the gaps/scoring.

Now on the desperate hunt for a new calliper.

 

[02gf74]

hmmm.... i suspected that could happen. Better to have that happen now than when out cycling. Can you get pistons and seals?....most likely be cheaper to pick up sh one off ebay.


Try madison co uk for spares.

 

[ishaw]

I don't think they do spares, but worth an ask I guess.