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  1. #1
    WooHoo Biking!!!!
    Reputation: goodvibe's Avatar
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    XT Disc Brakes and cold weather.

    Greetings All!
    I have XT Hydraulic Brakes on my Trek Remedy and I have been having an issue with them when the temperature gets cold. When my bike is in my basement, the brakes work great and I have a little bit of a stroke before the brake grabs the caliper. They work great in the warm temperature.

    I went riding today and after the car ride to my destination (with my bicycle on my exterior rack) my brakes are very tight. It seems like the mineral oil inside expanded somehow in the cold. Does anyone else have this issue? If I were to put brake fluid in the brakes would it destroy the rubber seals inside? Do they sell a seal kit that would accept regular brake fluid?

    Any ideas?

  2. #2
    ride hard take risks
    Reputation: dogonfr's Avatar
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    You will find that some brakes, components or suspension work better than others yet not being brand or model specific. Fred may have no issues yet Alfred has nothing but problems with the same product in the same neighborhood on the same days.

    No you cannot replace Mineral for DOT fluids and no manufacture offers a conversion kit.

    Adjust your riding style to meet the conditions.
    Formotion Products
    http://www.formot

  3. #3
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    Quote Originally Posted by goodvibe
    Does anyone else have this issue?
    Do you have the 08 XT's (770 series)? I have the same issue with mine, this is a common problem with the 08 XT's. It's not the mineral oil expanding, it's the piston seals that are making the pistons sticky. I heard that Shimano has revised the rubber in the seals to make them more winter-friendly. I personally still have to send my calipers in for a new set of seals, I've just been living with it for a while.

  4. #4
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    I know some riders having that problem and I myself had a similar one but from a different cause. Don’t use any other brake fluid, even other mineral oils don’t work too well with those brakes and can effect the seals.

  5. #5
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    Reputation: itsdoable's Avatar
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    We've had this issue with pretty much all brands of brakes at one time or another, mineral oil or DOT.

    The issue is always the makeup of the piston seals, in cold weather the seals get stiff, and do not bend and recover well. The recovery of the seals (after bending) is responsible for retracting the pistons at the caliper. When they get stiff, they don't retract the pistons. The QA on the seals seems to vary from batch to batch, and some manufacturers are more careful specing the seals than others. Most will warrenttee the problem.

    Do not put DOT fluid into a system designed for mineral oil.

  6. #6
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    As said this is a known problem with many 08XTs. The german bike forum shows a lot of XT users with the same issue.

  7. #7
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    When you sent them back, did you bring them to your LBS, or did you send them to shimano? Should I call Trek? Do you think that they will do anything?

  8. #8
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    Quote Originally Posted by goodvibe
    When you sent them back, did you bring them to your LBS, or did you send them to shimano? Should I call Trek? Do you think that they will do anything?
    goodvibe if you're referring to me, I haven't sent them back, I still have the original seals. I would bring them back to your LBS, they'd be the ones to handle warranty issues.

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