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Thread: Magura MT8 fail

  1. #1
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    Magura MT8 fail

    Today was the second time in a month that my MT8's lost all stopping power on my rear brake. The first time was the first ride after mounting them We had cut the lines, but they had been fine while I was bedding them in on the hill where I live, then on the trail they slowly lost all stopping power. it was a cold (teens) day. I figured they just needed to be bled, so I managed to bleed them using a fitting from my Avid kit.

    I've been riding them 3 times a week for 2-3 weeks without any problems. Then they quit again today, temp was 7 at the start of the ride. WTF??? The front brake was fine (thank God).

    So I bled them again tonight, figured I'd be all set since I bought a Magura bleed kit., and in the process found out that the kit doesn't provide you with the o-ring necessary for the caliper fitting. Grrrrr. Had to resort to the avid fitting again. Why sell something that is unusable out of the box???

    Anyone else have a similar issue with the MT8's? I checked all the fittings for signs of leakage and they were all dry. I was thinking maybe it had something to do with the cold, but the front has been fine.

    If it happens one more time it's going back.

  2. #2
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    Update: Called Magura USA regarding the o-ring. They said no o-ring is needed, but they'll send me a few anyway. I told him snugged it up pretty good but didn't want to over-torque it, and it was sucking air when I tried to draw the fluid back.

    Regarding the failure, my LBS is thinking its the cold, said some Shimano brakes suffer from seals shrinking in extreme cold and letting fluid pass. But my front brake was fine, well maybe it was fading a bit on the downhills, I attributed that to it getting too hot having to do all the work.

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    My bleed kit didn't have any parts for the caliper at all. Had to buy the dealer kit before I could bleed the brakes. Haven't had problems since, though.

  4. #4
    gran jefe
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    as much trouble as people have with bleeding, it makes me wonder when bike calipers will start to come with bleed screws like on cars.

  5. #5
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    It's definately the temp. Most all brakes are known to have issues in such extreme temps. Put the bike away and the snow/ice gear out, LOL!

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    Quote Originally Posted by Bill in Houston View Post
    as much trouble as people have with bleeding, it makes me wonder when bike calipers will start to come with bleed screws like on cars.
    They do.

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    7K or 7F or 7C :-)
    if my feet get cold after 30 minutes of riding...then it is too cold. Even my xtr vbrakes don't like cold.

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    gran jefe
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    Quote Originally Posted by the-one1 View Post
    They do.
    Really? With a tubing fitting? Why do I see bleed instructions like "ziptie down the brake lever and leave it overnight and hopefully in the morning the bubbles will have floated out the top?" If they had the tubing fitting, you could just recycle the fluid until the bubbles were all out. I definitely haven't seen anything like that. But maybe I'm not paying enough attention.

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    Quote Originally Posted by ambassadorhawg View Post
    It's definately the temp. Most all brakes are known to have issues in such extreme temps. Put the bike away and the snow/ice gear out, LOL!
    That ain't gonna happen.

    And my front brake was fine, so I'm thinking maybe an issue with the rear brake.

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    Quote Originally Posted by Bill in Houston View Post
    Really? With a tubing fitting? Why do I see bleed instructions like "ziptie down the brake lever and leave it overnight and hopefully in the morning the bubbles will have floated out the top?" If they had the tubing fitting, you could just recycle the fluid until the bubbles were all out. I definitely haven't seen anything like that. But maybe I'm not paying enough attention.
    You talking about this little guy? Shimano, Hayes, Avid, Hope, etc... all have them
    Attached Images Attached Images  

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    Quote Originally Posted by the-one1 View Post
    You talking about this little guy? Shimano, Hayes, Avid, Hope, etc... all have them
    Wow, there you have it. Thank you. So I am left wondering why people have such problems bleeding their brakes. A question for another day. Thanks again.

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    Quote Originally Posted by Bill in Houston View Post
    Wow, there you have it. Thank you. So I am left wondering why people have such problems bleeding their brakes. A question for another day. Thanks again.
    That part doesn't determine how easy it is to bleed a brake, but the subject of this thread is the MT8 and it doesn't have that thing anyway. The problem I had with my initial bleed of the MT8 was the poor quality of the Magura bleed kit. You can't do it without the right tools.

  13. #13
    gran jefe
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    Quote Originally Posted by craigsj View Post
    That part doesn't determine how easy it is to bleed a brake, but the subject of this thread is the MT8 and it doesn't have that thing anyway. The problem I had with my initial bleed of the MT8 was the poor quality of the Magura bleed kit. You can't do it without the right tools.
    Yes, I apologize. I didn't mean to sound like it was your fault you are having a problem, or anything like that. It sounds like you got a bad deal and are left trying to work with something pretty sub-optimal.

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    Quote Originally Posted by Bill in Houston View Post
    Yes, I apologize. I didn't mean to sound like it was your fault you are having a problem, or anything like that. It sounds like you got a bad deal and are left trying to work with something pretty sub-optimal.
    The MT's have a port (like the Elixir's) on the caliper body. You unscrew a plug, then screw in the fitting that is attached to a tube going to a syringe. In my case, the fitting is not seating completely and is allowing air to be drawn into the tube when pulling on the syringe plunger to pull the oil back out.

    I know that some of the other systems (the type that have a reservoir on the lever body) have a port that you simply loosen the valve and attach a tube. This is not one of those.

  15. #15
    gran jefe
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    Quote Originally Posted by dirtyjack View Post
    The MT's have a port (like the Elixir's) on the caliper body. You unscrew a plug, then screw in the fitting that is attached to a tube going to a syringe. In my case, the fitting is not seating completely and is allowing air to be drawn into the tube when pulling on the syringe plunger to pull the oil back out.

    I know that some of the other systems (the type that have a reservoir on the lever body) have a port that you simply loosen the valve and attach a tube. This is not one of those.
    Instead of pulling the syringe, what if you squeeze the brake lever, and force oil into the syringe?

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    Discontinue Gustav. Hello MT8. Now that's progress

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    Quote Originally Posted by Bill in Houston View Post
    Instead of pulling the syringe, what if you squeeze the brake lever, and force oil into the syringe?
    I don't think that would draw the oil from the top syringe back into the system.

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    Quote Originally Posted by dirtyjack View Post
    In my case, the fitting is not seating completely and is allowing air to be drawn into the tube when pulling on the syringe plunger to pull the oil back out.
    Is there any chance you aren't torquing the fitting enough?

    I had no problem with mine (mt 6's, but they have the same bleed port set up) sucking air in at the fitting when I bled (had to bleed to to screwing up shortening the line on the front brake). I agree that the quality of the bleed kit leaves a bit to be desired. I was worried it would draw air in between the tube and syringe. Avid's kit blows this out of the water (but then it costs a lot more money).

    In any event, unless there is a torquing issue, it seems that if there is a machining issue in the caliper not allowing the bleed fitting to seal, it seems that there are going to be problems with the brakes letting air in at that bleed port, no matter what.

    Hope you get them sorted out. I know I love my MT-6's, and even though they were expensive, I don't regret upgrading from the Elixir 5's.

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    @dirtyjack: Brake lever bottoming out with little bite resulting on the caliper end?
    -Greg
    Lynskey Ridgeline 29-SL, Truvativ Hammerschmidt, Cannondale Lefty 29er SL w/ DLR (Project321 adaptor). 26 lbs.

  20. #20
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    Quote Originally Posted by dirtyjack View Post
    The MT's have a port (like the Elixir's) on the caliper body. You unscrew a plug, then screw in the fitting that is attached to a tube going to a syringe. In my case, the fitting is not seating completely and is allowing air to be drawn into the tube when pulling on the syringe plunger to pull the oil back out.
    How would you feel about putting a bit of teflon tape on that fitting?

  21. #21
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    Quote Originally Posted by Goannaman View Post
    Is there any chance you aren't torquing the fitting enough?

    I had no problem with mine (mt 6's, but they have the same bleed port set up) sucking air in at the fitting when I bled (had to bleed to to screwing up shortening the line on the front brake). I agree that the quality of the bleed kit leaves a bit to be desired. I was worried it would draw air in between the tube and syringe. Avid's kit blows this out of the water (but then it costs a lot more money).

    In any event, unless there is a torquing issue, it seems that if there is a machining issue in the caliper not allowing the bleed fitting to seal, it seems that there are going to be problems with the brakes letting air in at that bleed port, no matter what.

    Hope you get them sorted out. I know I love my MT-6's, and even though they were expensive, I don't regret upgrading from the Elixir 5's.
    Possibly, but I'm not going to over-torque it trying to get a seal, when a simple o-ring will solve the problem.

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    Quote Originally Posted by grnamin View Post
    @dirtyjack: Brake lever bottoming out with little bite resulting on the caliper end?
    Yes, when they failed, it was lever to the bar and zero braking.

  23. #23
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    Quote Originally Posted by Bill in Houston View Post
    How would you feel about putting a bit of teflon tape on that fitting?
    Shouldn't be necessary. The o-rings should do the trick.

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    Quote Originally Posted by Bill in Houston View Post
    Well, yeah, it SHOULD, but I thought we were trying to figure out how to keep you from smacking into something.
    I was able to bleed them using the fitting from the Avid kit, and I've been riding a couple times since and it's back to normal. Next time (and I hope it's not for a long time) I have to bleed them, I'll have the right o-ring on the Magura filling, so it should be fine.

  25. #25
    gran jefe
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    Quote Originally Posted by dirtyjack View Post
    Shouldn't be necessary. The o-rings should do the trick.
    Well, yeah, it SHOULD, but I thought we were trying to figure out how to keep you from smacking into something.

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