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Thread: avid mech disc adjustment

  1. #1
    []D [] []V[] []D chasten's Avatar
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    avid mech disc adjustment

    okay...

    just installed a set of used avid mechanical disc brakes (front and rear). the pads are like new, the rotors are straight. following the avid tech manual's installation instructions as far as setup goes...

    the rear brake is purrrrfect. i had to adjust it a little bit, but it's awesome now. the front is not. it's totally spongy-like. i have to squeeze the hell out of it to get it to lock up. this is not how it is supposed to be. i've adjusted the pads all over the place, and am convinced that the problem is probably something else.

    any quick fix ideas? on a car, we'd replace the pads and put a non-directional refinish on the rotors. i don't want to replace the pads, if i don't have to... anyway... some help?
    chas∑ten
    Function: transitive verb
    1 : to correct by punishment or suffering
    2 a : to prune (as a work or style of art) of excess, pretense, or falsity
    b : to cause to be more humble or restrained
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  2. #2
    try explaining the internet to a bum!
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    carlos's Avatar
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    spongy?

    could be a few things.

    -check your brake lever for excessive pivot slop. old levers develop slop and typically, you'll have to toss them.

    -make sure you used the proper housing. there are two types of 5mm housing. one for derailleur and one for brake. with a light held up the the black surface, you'll see ribbing, if it's brake housing.

    look closely...if not, then it's derailleur....which actually should give a more stout feel.

    -also, if it is brake housing it's going to need to be compressed, both now, and over time.

    one easy way to speed this up is to turn the barrel adjuster on the brake lever until about 5 or 6 threads show.

    then, check to make sure the cable fixing bolt on the brake is nice and tight...don't want that cable to slip.

    ok, now go back to thebrake lever and squeeze it hard enough to touch the grip. yeah....that hard. it proabably won't touch the grip but you get the idea.

    -since you've checked that you rotor is straight and that the pads are new.....also consider checking the alignment of the pad to the rotor. if they don't hit square the brake will feel weak.

    -check and make sure the housing is properly seated in the metal ferrules at the end of each piece of housing.

    are you using v brake levers? if you're using canti levers you'll have to get rid of them and use v brake levers. cantis won't work witht he Avid disc brakes.

    that's all i can think of for now but let me know if any of this helps.

  3. #3
    mOjO cHaUfuRr toonces's Avatar
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    I love the way Avids setup; quick and firm. Lots of clearance for rotor warpage and good dialing. Did you take all the slack out of the cable? Adjust the red knobs to get the right pad clearance? You might also check to make sure there's no gunk on the rotor. If it's really spongy, see carlos's post. Maybe cut the housing shorter if you can. Hmm... otherwise, you'd better let me test ride your bike for a few days and i'll figure out what's wrong. Just remember dents and scratches add character.

  4. #4
    []D [] []V[] []D chasten's Avatar
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    thanks for the advice, guys...

    actually, i've already done all of the stuff suggested EXCEPT realigning the pads. i'll try that next... thanks so much for the help, guys.

    toonces... any time you want to take the hotrod for a spin, you've got my blessing. just remember that that door's going to have to swing both ways, Hun. heh heh..
    chas∑ten
    Function: transitive verb
    1 : to correct by punishment or suffering
    2 a : to prune (as a work or style of art) of excess, pretense, or falsity
    b : to cause to be more humble or restrained
    -
    -
    (0011 0000 0011 1000 1000 0100 0010 1000 0010 0011)BCD
    -

  5. #5
    MoJocephus watmatt's Avatar
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    I had the exact same problem with mine the first go around. I was about to call Avid and ask them about it, it was so bad. I didn't, just put it away for the day and picked it up the next day. I just kept at it and after a bit it just fell into alignment. It was a combination of cable and pad adjustment. Not sure exactly what I did different from the day before (to much blood in the alcohol system?) but it worked.

    One thing that I did do, (Iím pretty sure itís not supposed to be this way, but it works ) is I moved the actuator arm (to squeeze the pads closer) about ľ in. up the cable before locking it down. So this way the arm never fully retracts. This moved the pads closer to the rotor and tightened it up considerably. There is still plenty of clearance for the arm to fully clench the pad with out toping out at the caliper housing.

    Give it another shot, I'll bet you get it.
    "You take a bad boy and make him dig holes all day in the hot sun and it turns him into a good boy." - Mr. Sir

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