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  1. #1
    mtbr member
    Reputation: Rusty Shackelford's Avatar
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    New fork now brake issues

    I just put on a new fork the only real difference is i went from an IS mount to a post mount but now i have real bad brake rub. I am thinking of doing a brake bleed but want to avoid it since one was done about a month and half ago. Any other suggestions? I tried pushing the cailbers back in and re seating the brakes but it still rubs.

    Thanks all

  2. #2
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    Reputation: winter's Avatar
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    Brake rub is generally not an indication for bleeding hydraulic brakes. The culprit is probably improper caliber alignment or improper seating of the brake pads within the caliper. If this is the case, then it's simply a matter of proper shimming and adjustment of the caliper body; this can take some time, trial and error, and use of profanities, but it can be done.

    The other possibility is that during the switching over, you accidentally advanced the pistons in the brake caliper; as a result there is now less space between the two brake pads. The solution in this case is to remove the brake pads and push the pistons outward with a screw driver (you can also do this with the brake pads in place, but you risk contaminating the pads).
    Go on ahead, I'm gonna take a breather.

  3. #3
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    He went from IS -> PM. IS is the one w/ the shim. For PS you just sort of loosen the bolt and push the caliper around.

  4. #4
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    I adjust my PM calipers by loosening both bolts just enough so that the caliper can easily move side to side. Then I apply the brake lever, which should perfectly center the caliper over the rotor if both pistons are extending and retracting properly. Holding the lever, I carefully tighten the bolts making sure I don't alter the position of the caliper in the final cinch. Sometimes I have to repeat this process a few times before finding the perfect position, but It pretty much always gets rid of rub.

    If the above procedure isn't working, then you may have a poorly retracting piston, often caused by dirt and brake dust. Not sure what brakes you have, but my Martas have a procedure called "unsticking a stuck piston" which I have had to follow a few times. It's a pretty common sense procedure, nothing special really. I'm sure it's on the Magura website, but not sure how well it works with other makes.

    The last thing that may enter the equation if none of the above works for you is shimming the rotor out on the hub. Special shims are available for this, but if this is needed, I would try to identify why you really have to do this as it could be an indication of some other issue with the caliper and/or mounting.

    Remember, a properly operating brake system should have zero rub....so keep looking for the cause. I doubt it has anything to do with a brake bleed, unless you are experiencing other symptoms of having air in the lines (spongy lever feel, poor stopping power, etc)

    Good luck.

  5. #5
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    Quote Originally Posted by Betarad View Post
    I adjust my PM calipers by loosening both bolts just enough so that the caliper can easily move side to side. Then I apply the brake lever, which should perfectly center the caliper over the rotor if both pistons are extending and retracting properly. Holding the lever, I carefully tighten the bolts making sure I don't alter the position of the caliper in the final cinch. Sometimes I have to repeat this process a few times before finding the perfect position, but It pretty much always gets rid of rub.

    If the above procedure isn't working, then you may have a poorly retracting piston, often caused by dirt and brake dust. Not sure what brakes you have, but my Martas have a procedure called "unsticking a stuck piston" which I have had to follow a few times. It's a pretty common sense procedure, nothing special really. I'm sure it's on the Magura website, but not sure how well it works with other makes.

    The last thing that may enter the equation if none of the above works for you is shimming the rotor out on the hub. Special shims are available for this, but if this is needed, I would try to identify why you really have to do this as it could be an indication of some other issue with the caliper and/or mounting.

    Remember, a properly operating brake system should have zero rub....so keep looking for the cause. I doubt it has anything to do with a brake bleed, unless you are experiencing other symptoms of having air in the lines (spongy lever feel, poor stopping power, etc)

    Good luck.
    Thank you Betarad. After messing around with it for about an hour i tried your method and it worked flawlessly.

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