Results 1 to 18 of 18
  1. #1
    mtbr member
    Reputation:
    Join Date
    Nov 2004
    Posts
    393

    Front brake on long downhills is gettin out farther and stiffer, XTR 2007

    Cannondale Carbon Rush 1 with XTR brakes.
    On long downhills the lever gets farther out and the brake stiffer.

    I have had the bike for 4 months and this is happening just recently.

    Any ideas?

  2. #2
    LBS Manager
    Reputation: Johnny Hair Boy's Avatar
    Join Date
    Jul 2004
    Posts
    1,890
    It sounds like the fluid is heating up and expanding.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Nov 2004
    Posts
    393
    So a fluid change will solve this?
    WHat kind of fluid should I use?

  4. #4
    mtbr member
    Reputation: rjpstoked's Avatar
    Join Date
    Jan 2004
    Posts
    347

    air?

    a tiny amount of air might also be a cuprit

  5. #5
    mtbr member
    Reputation: Carbon Ken's Avatar
    Join Date
    Mar 2005
    Posts
    691
    So this problem only occurs on long descents?

    ie. The lever action returns to normal afterwards or on level terrain?

    If so, it isn't a matter of air getting into your system. It sounds more like brake fade in which case you may want to consider a larger rotor up front if you continue to do huge descents. I don't think the XTR's were made for downhill riding.

  6. #6
    Vaginatarian
    Reputation:
    Join Date
    Oct 2005
    Posts
    5,685
    Quote Originally Posted by motoadve
    So a fluid change will solve this?
    WHat kind of fluid should I use?
    the only fluid allowed is mineral oil, and shimano says only theirs.
    I believe it changes color if it gets overheated (should be red)
    if it is overheating a bigger rotor , like posted here, should help

  7. #7
    Vaginatarian
    Reputation:
    Join Date
    Oct 2005
    Posts
    5,685
    Quote Originally Posted by Carbon Ken
    So this problem only occurs on long descents?

    ie. The lever action returns to normal afterwards or on level terrain?

    If so, it isn't a matter of air getting into your system. It sounds more like brake fade in which case you may want to consider a larger rotor up front if you continue to do huge descents. I don't think the XTR's were made for downhill riding.
    didnt know there was a specific DH brake caliper

  8. #8
    mtbr member
    Reputation: FlatFender's Avatar
    Join Date
    Aug 2006
    Posts
    662
    Quote Originally Posted by dan0
    didnt know there was a specific DH brake caliper
    not caliper.... rotor.

  9. #9
    Vaginatarian
    Reputation:
    Join Date
    Oct 2005
    Posts
    5,685
    Quote Originally Posted by FlatFender
    not caliper.... rotor.

    I know, I was replying to Carbon , He said xtr wasnt made for DH

  10. #10
    mtbr member
    Reputation:
    Join Date
    Nov 2004
    Posts
    393
    After the long downhills the lever returns back to normal.
    But I have been doing the same downhills for the last 4 months and its just now that I get the problem.
    So should be able to solve it and be back to normal, thats why changing a rotor is too dramatic of a change since it was working fine before.

  11. #11
    LBS Manager
    Reputation: Johnny Hair Boy's Avatar
    Join Date
    Jul 2004
    Posts
    1,890
    If the lever is pumping up and getting firmer on long down hills the only thing that makes sense to me is fluid expansion. You can probably get rid of it with a larger rotor like others have said. I you do not want to do that you could try Magura mineral oil. Shimmano would frown on this and probably void your warrenty but I think it is a far better fluid.

  12. #12
    mtbr member
    Reputation:
    Join Date
    May 2006
    Posts
    11,138
    The 07 XTR levers (don't know Dual Control), have a small bleed port that can allow both oil and air to escape from the master cylinder suction, when the lever is not applied.

    If the problem is fluid expansion than allowing the lever to fully extend should allow the excess fluid to return to the reservoir. (maybe hard to do given the terrain).

    Are the pads worn? This would allow somewhat more heat to get through the pad to the caliper.

    I cooked my pads, on a downhill a few weeks ago. The rotors did not warp but I had to resurface the rotors, to get the brakes with the new pads to stop warbling.

    The rotor I had was LX and is wider than the XTR rotor, so you could actually feel the ridge where the rotor had worn out.

    Bigger rotors should help as well.

  13. #13
    mtbr member
    Reputation:
    Join Date
    Jul 2006
    Posts
    2,284
    Quote Originally Posted by dan0
    didnt know there was a specific DH brake caliper
    Yes, they are usually a little more powerful and dissipate heat better, but at the cost of weight. That being said, most people are fine with standard Juicy's.

  14. #14
    ballbuster
    Reputation: pimpbot's Avatar
    Join Date
    Dec 2003
    Posts
    12,624

    Overfilled?

    Quote Originally Posted by motoadve
    Cannondale Carbon Rush 1 with XTR brakes.
    On long downhills the lever gets farther out and the brake stiffer.

    I have had the bike for 4 months and this is happening just recently.

    Any ideas?
    If the reservior is overfilled, the fluid will have nowhere to go when it expands. I had the problem with my Hope Mono Minis. Turns out I was filling it before retracting my pads all the way. On the Hopes, you;re supposed to bleed and fill the brakes with the pistons shoved all the way in. When the pads are then adjusted to the correct position, it sucks the accordian reservior bladder in to compensate. Check the manual on your XTRs, but I suspect they are the same idea.

    This is also assuming that you have no air or water in your brake lines.

    Also, if you keep a finger on the brake for an extended period of time (riding your brakes, as they say), the fluid will expand between the master cylinder piston and the caliper without any room to burp into the reservior, causing the buildup up you describe. When braking, its better to hit your brakes harder for shorter amounts of time, then release them all the way to let them cool off.

  15. #15
    mtbr member
    Reputation:
    Join Date
    Nov 2004
    Posts
    393
    Maybe water?
    Its very wet and muddy where I ride.
    Will check for air too.

    Reservoir has never been opened so is not overfilled.

    Thanks guys

    Thanks

  16. #16
    LBS Manager
    Reputation: Johnny Hair Boy's Avatar
    Join Date
    Jul 2004
    Posts
    1,890
    Quote Originally Posted by motoadve
    Maybe water?
    Its very wet and muddy where I ride.
    Will check for air too.

    Reservoir has never been opened so is not overfilled.

    Thanks guys

    Thanks
    It could have been overfilled from the factory.

  17. #17
    mtbr member
    Reputation:
    Join Date
    May 2006
    Posts
    11,138
    Just opening the cap and a quick dip should relieve an overfill problem. But I havn't been able to overfill mine yet

    Maybe there is some dirt or something in the bleed port??? you can see when you take of the rubber diaphragm, right on top of the cylinder where it sticks into the reservoir.

    Bleed a little bit of fluid out the caliper port and see if it is discoloured, if so get a bleed kit and exchange fluid.

  18. #18
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    258

    Mine Too !

    first few weeks no problems(not as strong as old Juicys though), but past few weeks (warm,dry, more descents) front brake pumps up and drags until it cools down. (Makes clicking&popping sounds while doing so) I'm 150lb XC guy, 6" front and rear, on 29er. I bought 185mm Front rotor and adapter, but not put it on yet...I also used to have 765XT brakes, worked fine, never had problems. Thining about going back to Avid, but my hubs are Centerlock and I'm not willing to do the adapter thing again...any other ideas/advice?
    that rug really tied the room together.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •