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  1. #1
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    Can brakes lose their ability to "return" over time?

    somewhat older Rear Marta (IS caliper, IS mount) on HT 29er.
    I've been running them without any rear problems for half a year. (ever so slight, but liveable rub)
    I was getting some uneven rub so I took the rotor off and trued it. I also noticed one of my pads was heavily worn while the other was not (indicating that the rotor was rubbing on one side) I switched the badly worn bad with another I had off of my other bike.

    Now no matter how I adjust it, the rotor "rubs" on the pads. The rotor spins freely...if you had ear plugs in, you wouldn't know its scrapping. No matter how I adjust it I can't get it to spin without noise. I trued the rotor just to double check it and it seems true. (the noise is even and consistent) And tried another rotor, same problem.

    My only thought: Can brakes lose their ability to "return" over time? The rotor appears to be centered between the pads, they just seem to not open back up enough.

    thoughts??

  2. #2
    I Tried Them ALL... Moderator
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    Stuck pistons, due to accumulated dust and grime. Martas always return back, due to their auto pad adjustment...time to detail your brake calipers with alcohol and a Q-Tip.
    "The mind will quit....well before the body does"

  3. #3
    Spring! Spring! Spring!
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    Magura also has a process documented to clear up pad-return issues, check the tech-docs on their web site for your brake.

  4. #4
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    Did you....

    reseat the pistons into the caliper before you installed the newer pads? This is done with a medium sized screwdriver or something similar. You insert it between the pads and gently twist until both pistons are completely seated in the caliper. Then once the wheel is reinstalled you simple give 4 or 5 firm squeezes at the lever to readjust. New or newer pads are thicker and hydraulic brake calipers automatically adjust for pad wear. As the pads wear the pistons move a bit further out to compensate. If you don't reseat them before installing new pads then they stay in the extended position and rub. Try this first, if you haven't already, and see if it solves your problem. If not then you could have a sticky piston. In which case, removing the pistons, cleaning and lubing the seals then reinstalling will solve the problem. Also you could have to much fluid in the system as well. If the breaks were bled without reseating the pistons as above before the bleed, you could have to much fluid in the system which would not allow them to retract fully when the lever is released.

    There can be other problems as well, but the above are the most likely. From what you describe though, I'd say the first is most likely the culprit.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  5. #5
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    Sticky pistons of course...

    Also the return spring loses strenght over time...

    Clean pistons get new pads and a spring.

  6. #6
    Spring! Spring! Spring!
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    Quote Originally Posted by jeffscott
    Also the return spring loses strenght over time...
    I don't think the maggies use return springs, maybe in the lever assembly?

    At the caliper, the seal/lip has a bit of return to it, but that's it as far as I know.

  7. #7
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    Quote Originally Posted by bear
    I don't think the maggies use return springs, maybe in the lever assembly?

    At the caliper, the seal/lip has a bit of return to it, but that's it as far as I know.

    Well there you go no return spring....

  8. #8
    Spring! Spring! Spring!
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    Quote Originally Posted by jeffscott
    Well there you go no return spring....
    yeah, i've had a love-hate relationship with that concept for the last 7 years (I've been running Louise FR brakes since '03 and have them on two bikes).

    The maggies don't seem to naturally open up as wide (piston-wise) from the rotor as some others like the Avid, which makes them more vulnerable to drag/noise if your rotor isn't true.

    OTOH, I can count on one hand the instances where this has been a problem or bother to me, and I've only had to replace one rotor from crash damage the whole time. I've also never had a problem because the spring got caught up in the mechanism from crash or crud. I've also never had a problem with a lost spring after pad changes.

    "Meh" - I think it comes down to personal preference.

  9. #9
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    Thanks for some of these tips.

    When I put in the new pad, I opened up the gap between them before I put the wheel back on, but I may have not returned them fully into the caliper. I 'll first try that, then give the pistons some attention. (although I've never done that before, I'm guessing I can figure it out!)

  10. #10
    Spring! Spring! Spring!
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    any time I change the pads I check the re-centering. usually it's no change, but now and then there's a minor tweak. I've never bothered to chase down why.

  11. #11
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    I'm going to try this:
    http://www.magura.com/uploads/media/...ilisierenE.pdf

    could my seal/lip benefit from some sort of lubricant? (I'm in arid New Mexico) if so, what would you use?

  12. #12
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    Silicone spray and wipe away excess so as to not attract dirt.

  13. #13
    I Tried Them ALL... Moderator
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    Guys, Magura Marta does not have clips, springs or anything that can be lost. The pads and levers retract by good ole' hydraulic "memory."
    "The mind will quit....well before the body does"

  14. #14
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    just thought I'd give a quick update to let you know that your suggestions seemed to work. I pulled off the wheel and moved the pistons back and forth with a rotor, then cleaned up the seal/lip with some WD-40. Once I did that, my rotor was no longer centered, so I took out a shim. Seems to be good now. Might also explain my extreme uneven pad wear.

    thanks again!

  15. #15
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    I went through all this with my Martas after `4,000 miles, scrubbing a toothbrush, pushing the pads in and out repeatedly, finally soaked my calipers with Royal Blood overnight to try to loosen up grime. They never really got their "powers of retraction" back. I think part of the problem was worn out Delrin bushings at the levers, which was hanging up lever travel as well. I was supposed to send the brakes into Magura's US repair facility and wait for a rebuild and bill... but I didn't want to wait so I just bought new brakes. Maybe now I'll send them in, since I can ride my bike while i wait.

  16. #16
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    I also use a thin strip of fine grit sand paper to take the grime off the pistons with basically a "flossing" motion. Usually one or the other needs it. Then lube the piston before carefully stuffing it back into the calliper, then cleaning off excess mineral oil and exercising the stuck one by holding the good one in with a screw driver and pumping the stuck one out, stuffing it back in, pumping it out, stuffing...etc. Works every time but it's a huge PITA.

  17. #17
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    Quote Originally Posted by SJDude
    I also use a thin strip of fine grit sand paper to take the grime off the pistons with basically a "flossing" motion. Usually one or the other needs it. Then lube the piston before carefully stuffing it back into the calliper, then cleaning off excess mineral oil and exercising the stuck one by holding the good one in with a screw driver and pumping the stuck one out, stuffing it back in, pumping it out, stuffing...etc. Works every time but it's a huge PITA.
    I'm having the same problem, one side of my rear caliper is not fully retracting so it drags constantly on the rotor. I've tried the procedure recommended by Magura, but that didn't work. I've tried some superficial cleaning and dripping on Magura brake fluid; that seems to have helped a bit, but didn't fix it completely.

    But I haven't taken the piston out completely. How hard is it to replace it? Or maybe you weren't talking about taking the piston out completely? I figured that would be a pain, and require a complete bleeding.

    I might try the WD40 or silicone spray approach next, but so far it doesn't seem like it is freeing up very well. Is there something more that can or should be done to rebuild the caliper? Or is it just too old?

  18. #18
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    Ok no for sure don't take the piston all the way out. I'm pretty sure it would never go back in properly. So you take the pads out, you push the good piston all the way back in to the calliper. You lightly pry a large flat head screw driver against the GOOD piston and pump the brake lightly so that the BAD piston comes out to say hi.

    Note: if your reservoir is low you will suck air into the system and then need to bleed it so if you're not sure open the reservoir and check and top up as necessary.

    Try simply lubing the offending (BAD) piston preferably with Marta Blood. Second choice; shimano mineral oil. To me WD40 would be a DFL resort. Push the piston back into the calliper by alternating sides of the piston with your flat head screw driver. This action will cause the other piston to come out slightly. Repeat the process several times being careful not to over extend the piston. You'll know you are almost too extended cause the piston will start to go crooked. Baaaad!

    This is called "training the pistons".

    The whole "flossing the pistons" thing is one I came up with myself because sometimes stuff gets corroded and training is not enough. You're basically trying to loosen up the sticky piston so it moves more freely by sanding the outer sides of it with a thin strip of 150 or more grit sand paper. It's tough to do and kind of frustrating but it works. I use compressed air to blow everything out after and it really seems to help. Wear safety glasses for that part.

  19. #19
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    Quote Originally Posted by SJDude
    Ok no for sure don't take the piston all the way out. I'm pretty sure it would never go back in properly. So you take the pads out, you push the good piston all the way back in to the calliper. You lightly pry a large flat head screw driver against the GOOD piston and pump the brake lightly so that the BAD piston comes out to say hi.

    Note: if your reservoir is low you will suck air into the system and then need to bleed it so if you're not sure open the reservoir and check and top up as necessary.

    Try simply lubing the offending (BAD) piston preferably with Marta Blood. Second choice; shimano mineral oil. To me WD40 would be a DFL resort. Push the piston back into the calliper by alternating sides of the piston with your flat head screw driver. This action will cause the other piston to come out slightly. Repeat the process several times being careful not to over extend the piston. You'll know you are almost too extended cause the piston will start to go crooked. Baaaad!

    This is called "training the pistons".

    The whole "flossing the pistons" thing is one I came up with myself because sometimes stuff gets corroded and training is not enough. You're basically trying to loosen up the sticky piston so it moves more freely by sanding the outer sides of it with a thin strip of 150 or more grit sand paper. It's tough to do and kind of frustrating but it works. I use compressed air to blow everything out after and it really seems to help. Wear safety glasses for that part.
    Thanks for the comments! This is pretty much what I did, including using Magura Blood. I thought maybe WD40 would loosen things up more easily, but sounds like I should use Magura Blood. I hadn't thought of the "flossing" technique - there's not much space in there for my fingers! But it could be worth a try. At the least, I think I need to keep working ("training") and lubing the pistons. At first, I couldn't get the offending piston all the way retracted, but then it got easier, so maybe I gave up too soon!

  20. #20
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    I would not use 150 grit sand paper on the pistons. That is a fairly coarse grit. If I was going to lightly use an abrasive (not likely), it would be emery paper or 600 grit (or finer) paper.

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