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  1. #1
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    XTR Calipers won't retract

    I installed a set of XTR calipers last summer using my existing Shimano hyrdo levers. The installation went very well and they worked perfectly for months...no rub, no fade, no noise...they just plain worked.

    Up until a particulary crappy weather ride I took a week or so ago, that is...

    The pads sounded strange after the ride, so during the clean-up I remove them to inspect for wear...they seemed fine but after I put the pads back in I can't get the pistons to retract like they normally did...the brakes are rubbing all the time. Not just a little "zing-zing" rub where the pads kiss the rotor, but a full-on, slow the wheel down rub. Not all that noticable when riding, but enough to stop the rear wheel in a couple of revolutions when the bike is on the stand. I can manually push on the pistons or pads to open the caliper up, but they don't retract fully after I apply the brakes....I have repeated this exercise several times so it seems like I've got some maintenance to do.

    Can anyone suggest how to go about diagnosing and fixing this problem?
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  2. #2
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    If the Shimano system works like the Hope one, which I imagine it would, it's the seals that are responsible for retracting the pistons. How far they retract is relative to how far they've extended, which is why they are self-adjusting as the pad material wears. To reset the pistons on my Hope's when I fit new pads, I remove the reservoir cap and insert a little block of wood which is a tight fit between the pistons (11.5mm). I then replace the reservoir cap and pull the lever a couple of times. Because the block is wood it allows the pistons to extend minutely, but it seems to be enough to guarantee the seals will 'reset'.
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  3. #3
    JMH
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    Do a search... XTR calipers are notorious for this "feature". I had to finally get rid of a set because of the annoyance. Chuky's are okay but they sometimes show symptoms and I am just waiting...

    Tips that sort of help: don't let your brake pads wear down at all. Replace them when they are about 1/3 (or less) worn, and consider going with the metal pads if you are running resin. I found that the further the pistons are forced to extend, the less likely they are to retract. Also, when you pull the pads out, clean the pistons thoroughly with something gentle like rubbing alcohol and then lube them with a drop or two of mineral oil. I could sometimes get two or three rides with no sticking between cleanings.

    But mostly remember this: You are not alone, there are others like you and we share your pain and frustration, especially if it turns out you have one or more "chronic stickers"

    JMH

  4. #4
    Meh.
    Reputation: XSL_WiLL's Avatar
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    XTRs had some issues. The new ones seem to be better.

  5. #5
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    Will, baby...you're killing me here. You usually have all the answers, all the time and that is the best you can come up with?

    Seriously, thanks to everybody for your ideas. I'll try the clean-up suggested, then revert back to the friendly and most exellent wrenches at the LBS who are usually able to bail me out (and teach me something) when my own skills or knowledge leave me short. They were real high on the XTR's over the last couple of years so they may have some ideas on how to keep them running. FWIW, the set I am running are '06 calipers w/ resin pads. I'll also give the metallic ones a go.
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  6. #6
    Meh.
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    I gave up on the rubbing with the ones that came through the shop. I focused more on having them NOT HOWL. New rotors from Shimano, two different pads, and a little bit of squeel-stop on the pistons did the trick.

    You can reset the pistons with the method mentioned, but the brakes just really don't like to stay that way.

  7. #7
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    I thought I would close out this thread with a report on how thing worked out.

    First off, my front pads were pretty worn out. Not the worst I've seen, but they were ready for replacement. Based on the advice here and a quick consult with my LBS guys, I installed metallic pads and cleaned off the calipers and the section of the pistons that were exposed when I took the pads out. Not a thorough cleaning, just wiped out all the dust and crud I could get at. After that, the brakes worked much better but still exhibited a small bit of rub...this time just enough to hear but not enough to feel or make a big difference when the wheel spun down in the stand (given that the CK seals are doing their best to slow the wheel already).

    So I read up a little, and went at the pistons and seals again with some isopropyl alcohol and some q-tips. I extended the pistons pretty much all the way out (way more than they ever would during braking) by pumping them up--I could only get at one side a a time this way but it was easy to get everything very clean with the liberal use of the alcohol (on the bike, not for me). The pistons snapped back into their normal retracted position with a little persuasion from a lever (I used a large flat screwdriver and was careful where I was applying pressure).

    The brakes seem to be back to normal now--rub-free with instant engagement...very nice so far. They do howl more than before during braking but I attribute this to the metallic pads since I was using organic before.

    Note that I did not lube the the exposed surface of the piston, as others suggested. My hunch here is that the seals are supposed to keep the pistons clean and dry, and that any oil on the exposed surface of the brakes just accelerates the accumulation of crud.
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  8. #8
    JMH
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    The caliper that I used to oil from time to time was so far gone that I actually warranteed it through Shimano. Nothing worked.

    But I reckon I have had better luck leaving them dry also. A Shimano race-tech confirmed that hunch. Did you have to re-bleed when you extended the pistons? It is not unheard of that air will sneak into the system when you pump the pistons out for cleaning, so use care.

    Chuky's metal pads make a bit more noise than the resin, she hits them with the rubbing alcohol every month or so and that seems to do the trick.

    Glad they are working for you again... they can be SO finicky!

    JMH

    Quote Originally Posted by Dad Man Walking
    Note that I did not lube the the exposed surface of the piston, as others suggested. My hunch here is that the seals are supposed to keep the pistons clean and dry, and that any oil on the exposed surface of the brakes just accelerates the accumulation of crud.

  9. #9
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    I did not have to rebleed, but I might be lucky based on your comment. The shop guys said that rebleeding was good therapy for pads that had extended a bit too far, and I forgot about that when I pumped them all the way out. But they pumped right back up and feel great, so guess I dodged a bullet this time.
    Dad is sad.
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    He had a bad day.
    What a day Dad had!

  10. #10
    T95
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    I have been runniing XTR disc for several years and love them. As the pads ware it seems only one piston is applying the majority of the force. Here is how I remedy it:

    I suggest you start with a clean bike. Remove the wheel and throughly clean the pistons and calipers prior to resetting the pistons.

    Re set the pistons: I use the old pads and reverse them so I can apply a little pressure,with a screwdriver as you did, to the back side of the pads untill I re-seat the pistons.

    Reinstall new pad or the old pads correctly, and reinstall the wheel.
    Check the fluid level and top off taking care not to contaminate the resevoir with any debris from the cover. Reinstall the cover.

    Pull on the levers untill the pistons engage the pads and rotors. You may need to pump them several times. If the pistons are not exibiting equal movement in response to the lever then the system needs to be blead.

    Bleeding usually only takes a minute or so. I burp a drop of fluid out the bleeder while depressing the lever. It important to make sure not to release the brake lever with the bleed valve open. this will introduce more air into the system.
    When the pistons are responding evenly your set.

    I can get more detailed but I will leave it at that for now. good luck

  11. #11
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    I have been running the 06 XTR brakes all winter.

    The front as been very good, I do recenter it oh every two months.

    The rear has been wierd,

    Lots of recentering required to avoid drag, and sticky pistons, in addtion to some other problems not really related to the brake.

    It is getting much better now that the roads and paths are a lot cleaner, some of the sticky pistons seem to be due to dirt build-up.

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