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Thread: pulsing lever

  1. #1
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    pulsing lever

    i currently installed new brakes. all components new, brakes, discs, wheels. when braking, front brake i can feel lever pulsing slightly, unless i squeeze it harder than it stops. swapped pads, same thing. checked rotor, seems straight, unless it is just bent very slightly. thinking of replacing rotor unless i am missing something else. any idea?
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  2. #2
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    That there is the sign of a warped rotor. Same pulse would be felt if you had a warped one on your car. Contact your shop and have them warranty it.
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    Quote Originally Posted by brankulo View Post
    i currently installed new brakes. all components new, brakes, discs, wheels. when braking, front brake i can feel lever pulsing slightly, unless i squeeze it harder than it stops. swapped pads, same thing. checked rotor, seems straight, unless it is just bent very slightly. thinking of replacing rotor unless i am missing something else. any idea?
    Usually means uneven rotor thickness. Only takes a couple 10ths of a mm difference.
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  4. #4
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    things to look into can't give more info without having brands and types of brakes you installed.
    1. Warped rotor (as juancancook said)
    2. Grease/oil in a spot on the rotor (will usually just turn into no real brakes at all in no time)
    3. Crappy uneven rotor (as shiggy)
    4. Uneven brake in of new surfaces (kinda the same as the uneven rotor but can be fixed by just dragging the brake and go down a long hill)
    5. Loose caliper or rotor bolt.
    6. loose hub bearing (happens with Shimano hubs a lot if they aren't Adj right)
    7. Rotor backwards on hub
    8. Mis matched rotor to calipers (pads contact point being higher or lower or just all out bigger that the rotor's braking surface)
    9. Fork flex (really only on Carbon forks)
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  5. #5
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    brakes: 2012 xt, rotor: storm sl 203mm/160mm
    rotor looks dead straight, but if it only takes fraction of mm it could be it. nothing is loose, no shimano hubs, no fork flex. so other possibilities 7&8.
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  6. #6
    Trail Tire TV on blogger
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    Quote Originally Posted by brankulo View Post
    brakes: 2012 xt, rotor: storm sl 203mm/160mm
    rotor looks dead straight, but if it only takes fraction of mm it could be it. nothing is loose, no shimano hubs, no fork flex. so other possibilities 7&8.
    What fork? If you're doing XC type forks many are designed to take 160-180 max size ...
    Does it have a tab mount instead of a stud mount? many of the tab mount forks will flex the actual tab when there is that big of a rotor, too much torque for it.

    Also if you are using a Magura rotor I believe they have an odd contact surface location.. look at the rub marks and see it it's going into the arms of the rotor or going out all the way to the very outer edge...

    if everything seems good yo may just need to bed the pads properly.. go ride a long slight (not too steep) downhill and just drag the brake lightly, do it a few times and see if it goes away.
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  7. #7
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    talas 36, post mounts
    i think i did enough braking for it to bead during last week and weekend rides. rear one is working nicely.
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  8. #8
    Trail Tire TV on blogger
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    well, can't be much more help without having it in front of me... thing should work..

    check the wear and make sure the pads are hitting center of the brake surface on the rotor. maybe the pad isn't sitting right in the caliper? Rotor not centered in the caliper? just throwing stuff out there now.
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  9. #9
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    Quote Originally Posted by brankulo View Post
    brakes: 2012 xt, rotor: storm sl 203mm/160mm
    rotor looks dead straight, but if it only takes fraction of mm it could be it. nothing is loose, no shimano hubs, no fork flex. so other possibilities 7&8.
    Rotor warp (side to side movement as it spins) won't cause pulsing. As Shiggy said, its variation in rotor thickness. This won't be visible. You will have to use a caliper or micrometer to measure the thickness of the rotor in multiple spots around the braking surface. I had a brand new avid rotor that had a low spot that varied by .003" and it pulsed horribly. Got it replaced under warranty.

    The funny part is that I called SRAM first and the tech I spoke with claimed that .003" wasn't out of spec. I started laughing and politely said good bye.

  10. #10
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    Actually, a warp rotor will cause a pulse in the lever just as easily as uneven rotor thickness will. Key here is that under FIRM lever pull it stops. That shows that the warped area is being flattened out as it goes between the pads. Rotor thickness deviations will pulse constantly without regard to lever input force.
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  11. #11
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    it only pulses when braking lightly. i will replace it.
    thanks
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  12. #12
    bt
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    swap rotors front to rear and see if problem follows.

  13. #13
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    Mine was doing the same thing so i took my rotor off the wheel and set it on my kitchen table.. Mine is warped to hell from the kids opening the qr while it was on the stand and me not noticing until my brake locked up causing everything to bind up.. So basically I found mine was bent by setting the disk on a flat surface.. Maybe this will help you?
    Current Ride:2012 BAMF Full Nelson

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