[Deyv]

I took off the rear wheel to clean the bike and I could not get it back proberly without the disk rubbing heavily (wheel barely moving) . I played with the axel and QR just to make sure it was all the way in and it was. It seems that when I put the wheel in the disk is in the center of the pads but when I hit the brake to center them the disk is always stuck on the inside pad.

Took the pad off and 1 of them is pretty unevenly worn. Could that be it. I put 1 more spacer to reallign the calliper and it was fine until I hit the brake and then again the disk was stuck on the pad?

I will buy new pads later on , anyone has any other suggestions?

 

[Deyv]

BTW

anyone tried the metallic pad instead of the standard resing one?

 

[sub6]

from what I've heard lately, the XTRs have been having a LOT of problems with one piston not retracting evenly. That sounds like your problem.

I don't know how to fix it but I can say that you aren't alone in your suffering.


****HayesHayesHayesHayesHayesHayes****

 

[oldfart]

Try this: remove the pads and squeeze the lever to make the pistons stick out. Apply a little brake fluid to the sticking out edge of the pistons and push them back in. I read that some brakes had a problem with sticking pistons as they didn't get enough brake fluid onto the seals to lubricate them. Hayes have this problem some times too.

I'm using the metalic pads and not resin. Couldn't see any advantage to a pad that wore out fast and gripped less well.

I have also noticed with some hubs, XTR included, that centering of the rotor is dependant on the orientation of the axle. I assume it has something to do with the lock nuts on the ends of the axle not being perfectly square with the axle so it "cocks" the hub and rotor over ever so slightly to one side or the other. I had the same issue with Hayes brakes and XT hubs but the problem went away when I bought Hugi 240 disc hubs.

Once I center the calipers, I put a dab of paint on the axle and drop out so I can line them up after wheel removal.

 

[Deyv]

Originally posted by oldfart
Try this: remove the pads and squeeze the lever to make the pistons stick out. Apply a little brake fluid to the sticking out edge of the pistons and push them back in. I read that some brakes had a problem with sticking pistons as they didn't get enough brake fluid onto the seals to lubricate them. Hayes have this problem some times too.

I'm using the metalic pads and not resin. Couldn't see any advantage to a pad that wore out fast and gripped less well.

I have also noticed with some hubs, XTR included, that centering of the rotor is dependant on the orientation of the axle. I assume it has something to do with the lock nuts on the ends of the axle not being perfectly square with the axle so it "cocks" the hub and rotor over ever so slightly to one side or the other. I had the same issue with Hayes brakes and XT hubs but the problem went away when I bought Hugi 240 disc hubs.

Once I center the calipers, I put a dab of paint on the axle and drop out so I can line them up after wheel removal.

I thought you had to rebleed disk brakes when you hit the lever without the disk or pad in? you can push them back no prob?

 

[Deyv]

Thanks Oldfart

I found the same kind of advice directly from Shimano. They are suggesting to do it one at the time, would you see any reason to do so?

from shimano:

Assuming there are no air bubbles trapped behind the piston, We have seen a few XTR calipers that are experiencing this symptom. Due to the high machining tolerances and improved seals, the piston/caliper interface sometimes needs lubrication to assist in the initial break in period.
In order to lubricate the piston, the wheel and pads will need to be removed from the bike. Manually retract the pistons all the way into the caliper. Using an adjustable wrench and a clean rag to prevent marring of the caliper, stabilize one of the pistons while simultaneously pumping the brake lever very lightly to protract the opposing piston approximately 2-3mm. Using a light lubricating oil, place a small drop around the perimeter of the piston. Manually retract and protract the piston a couple of times to insure complete lubrication. Manually retract the piston and repeat on the opposite piston. Replace the wheel in the frame or fork. Center the caliper over the rotor. Re-install the brake pads and center the brakes by depressing the brake lever (pistons are self centering).

 

[oldfart]

That's what I read. I guess one could do both at once, but its best to follow their advice. There might be a reason to do it their way.

 

[Deyv]

Well I did what they suggested and it somehow worked. The piston was coming back normaly and the pads were not rubbing as bad(they were still rubbing a little)

But when I put back everything together I had a loose feel in the lever and could not pump it away, I opened up the reservoir and it was empty where did all the oil go?

Now I need to buy some oil and bleed them.

 

[Deyv]

Udpate:

I did the lubrification of the piston and it help a bit but the lever felt mushy so I bleed them. Better but not perfect. My pads were used a lot (I was almost grinding metal to metal) I changed my pads and it seem that the spring that comes with the new one is stiffer anyway with the lubrification of the piston, the bleed and new pads they feel perfect.