XTR rear disc brake

Kiara2K

Hi,

My XTR rear disc brake caliber or the piston (only 1 side) is not retrieving back fully after applying brake which caused the brake pad to constantly touching the rotor.
This caused some rolling resistent

When I removed the brake pads and pushed the piston back the rolling is very light but once I applied the brake, the rolling resistent comes back on.

Can anyone tell me why is this happening and how can I solve the problem.?

Thanks.

Marx SS

I ran Magura hydralic disks on my previous Avanti Barracuda & experienced that same prob. Rebleeding the system only helped alittle bit .
My prob was that the caliper did not sit evenly on both sides. One side it sat 1mm (approx) closer to the disk. The pads do retract alittle, but not enough to clear the disk on that one side. I tried to remount the caliper & spacing it out with washers from the frame mounts but that was the opposite of what I nedded ( for my alignment issue). I tried to file back the frame mounts of the caliper to reposition the caliper more centered & it kinda worked.

I suppose it is important to centre the caliper dead-on to take advantage of pads retracting when the brake is not applied. On most bikes this can only be achienved with spacing out or filing back the monuts, but it is difficult to make this even 90% of the time.
Can the bike shop help at all? They’re experts aren’t they?

Kiara2K

Thanks for sharing your experience.
Yes, once side of the piston is not retracting enough to clear the disk.
Although I can't hear the rotor scratching the pad but the rolling resistent is there.

I even switched the pistons from right to left position but the retracting problem moved to the left side instead.

We don't really have bike experts over here, another words is that what they can do I can do if only someone can advice me what I should do.

I bleeded it many times and as you mentioned it only helps a little.

HELP.......

daveornee

Are the pads centered about the rotor?
There are .2 mm adjusting washers to center them.
If they are centered, it sounds like you have a piston that is dirty or malfunctioning.
Take a look at the Shimano information attached about their front brake:

<http://xtr.shimano.com/tech_docs/BR-M965-F_SI.pdf>

I couldn't find a similar document for their rear brake... but there is an exploded diagram of the rear brake on their site.

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David Ornee, Western Springs, IL USA