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  1. #1
    Speed freak
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    Discs for Shimano XT

    I own a Felt Nine Pro (my first MTB), which came stock with the WTB Laser Disc Trail 29er. After a real heavy crash my front wheel is ruined. I bought a new set of Mavic C29SSMAX and wanted to shift wheels. What seems to be impossible is to move the discs from the old wheelset over to the new. The discs are bolted to the XT hub. What I need to do is get new discs and the question is; can I use any disc with the XT caliper or does it have to be the XT disc?

  2. #2
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    When you say impossible, do you mean you don't see how the rotors are attached? Are there 6 bolts holding the rotors or are there no visible bolts? If there are no bolts, it's a centerlock hub and rotor, you'll need a cassette lockring tool to loosen the rotor. Also, if the new wheels take 6 bolt rotors, you'll need new rotors anyway. I've used 160mm Avid rotors with XT 775 calipers no problem.

  3. #3
    Speed freak
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    @lyndonchen: I had a look at the discs/rotors and checked the Shimano website, and yes, its the center lock version. What I havent been able to figure out is if there are Shimano discs that are 6 bolt. I have checked this forum and there are those who advise to not to use a disc from Avid or any other manufactor than Shimano. I guess I am left with the choice of getting new brakes, levers, calipers and rotors.

  4. #4
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    Shimano does, or did, make 6 bolt rotors. Not 100% sure that the new brakes work with the old rotors though. The older Shimano brakes had a narrower track, so the old rotors may have a narrow track as well. Not sure.

    If you have the newer XT calipers, M775's, they will work with Avid and Hayes 160mm rotors. I have used both of these rotors and they're fine. If I remember correctly, the 185mm rotors from Avid will not work because of the 185/180 discrepancy. These are the Avid rotors:
    http://www.jensonusa.com/store/produ...ean+Sweep.aspx

  5. #5
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    Shimano still does make rotors, but they are "thinner" than most.

  6. #6
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    I'm reading your post differently then everyone else. I believe you are saying the old wheels are WTB Laser Disc Trail 29er's with WTB Laser Disc hubs.

    This is a 6 bolt hub and you need a T25 Torx wrench to remove the bolts. This is easy to do.

    You should also use a medium strength threadlocker (like Locktite 242) on the bolts when you install them on the new wheel.

    Or just take both wheels to your lbs and they should be able to do it in 5 minutes.

  7. #7
    Live 2 Ride
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    And charge you an arm and a leg...
    My Bike: '96 Gary Fisher Aquila
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  8. #8
    wyrd bi ful rd
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    come november this year it will be 2 years that i have had my XT775 with my Hope rotor ... no problems to date ...

    20080428 shimano xt 775 calipers MTBR FORUM.jpg

  9. #9
    Nightriding rules SuperModerator
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    Quote Originally Posted by the-one1
    Shimano still does make rotors, but they are "thinner" than most.

    the older shimano rotors, like the "old" 6 bolt rotor SM-RT75 have a narrow bracking track



    the current model centerlock rotors and, apparently, the new XT 6 bolt rotors SM-RT76 have a bit wider braking track


  10. #10
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    I meant thin as in the thickness of the metal.

  11. #11
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    I have two sets of XT brakes. One I use the SM-RT75 and on the other I use XTR. Both work great. If I had to choose one style though I would say I like the center lock better.

  12. #12
    Combat Wombat
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    Quote Originally Posted by Euro Trash
    I own a Felt Nine Pro (my first MTB), which came stock with the WTB Laser Disc Trail 29er. After a real heavy crash my front wheel is ruined. I bought a new set of Mavic C29SSMAX and wanted to shift wheels. What seems to be impossible is to move the discs from the old wheelset over to the new. The discs are bolted to the XT hub. What I need to do is get new discs and the question is; can I use any disc with the XT caliper or does it have to be the XT disc?
    You can find 6-bolt Shimano rotors fairly easy on ebay. As long as it is the correct diameter for your adapter, most other makes of rotors will work fine with your XT brakes. It is when you try to use the older Shimano rotors with their narrow brake track, with brakes other than Shimano, that you can have problems.

    If you are running M775 XTs, the calipers have not changed and you can run the older rotors.

    Brian

  13. #13
    Nightriding rules SuperModerator
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    Quote Originally Posted by the-one1
    I meant thin as in the thickness of the metal.

    really? I haven't measured "all brands of rotors" but the only ones I have found that are "noticeably" thinner are WW rotors like the Ashimas...and of course we are only talking a millimeter or so.....

    Anyhow, I don't think that the thickness variation is so great as to big problems....the braking path difference in thickness with the older shimano rotors might have a bigger impact.

  14. #14
    Speed freak
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    I bought rotors from BBB, However the left piston on the front caliper rubs on the disc and its kind of tough to ride... This was not the case with the old wheel and disc. What to do?

  15. #15
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    Quote Originally Posted by Euro Trash
    I bought rotors from BBB, However the left piston on the front caliper rubs on the disc and its kind of tough to ride... This was not the case with the old wheel and disc. What to do?
    Have you centered the caliper on the rotor? Changing wheelsets will usually require adjusting the caliper position.

  16. #16
    Nightriding rules SuperModerator
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    Quote Originally Posted by lyndonchen
    Have you centered the caliper on the rotor? Changing wheelsets will usually require adjusting the caliper position.


    Besides centering the caliper, one should also reset the pistons.

  17. #17
    Speed freak
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    OK guys. First of all, how do I center the caliper and secondly, how do I reset the pistons?

  18. #18
    Nightriding rules SuperModerator
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    To reset the pistons, you can use a CLEAN (as in no grease, oil on it, better clean it with alcohol) screwdriver to spread the pads apart; alternatively, you can remove the pads and use a plastic tire lever or some other "soft" tool and spread the pistons apart all the way back in the bore.

    To center the caliper just loosen the bolts, look in the slot and make sure the rotor is centered in the slot. You can do it "by eye", it might take a couple of attempts to get perfect, but it is worth it.

  19. #19
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    In addition to what crisillo says, see posts 11-13 here:
    Diff between lever reach and free stroke on XT?

  20. #20
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    Quote Originally Posted by crisillo
    really? I haven't measured "all brands of rotors" but the only ones I have found that are "noticeably" thinner are WW rotors like the Ashimas...and of course we are only talking a millimeter or so.....

    Anyhow, I don't think that the thickness variation is so great as to big problems....the braking path difference in thickness with the older shimano rotors might have a bigger impact.
    I'm just comparing the one's I have. 1 shimano, 1 Tektro, 1 promax, 1 unknown. The Shimano is thinner. Not that the thickness matters as mush as the braking track you're talking about. It's something I'm just putting out there as a "something to know".

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