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  1. #1
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    BB7 Front Brake ~ Fork Chatter

    Hello, this is my first post..so go easy on me. Riding a Specialized Hardrock Pro with (old I know) Judy 100TT front forks. Installed a new set of Avid BB7 185mm brakes, replacing the Shimano 160mm. I am a big rider, over 230lbs....on to the question.

    When I get on the front brake it grabs so strong that it seems like the fork is "chattering" or wiggling in the headset. The brakes still need to get past the break in period. The headset seems to be tight as are the mounting bolts for the BB7. Is there a fine tune to the BB7 to eliminate that or do I need to upgrade the fork?

    If I do need to upgrade the fork..any reasonably priced shock recommendation would be appreicated.

    Thanks in advance...

    Buellride in Madrid, Spain

  2. #2
    Meh.
    Reputation: XSL_WiLL's Avatar
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    What kind of rotor did the brake come with? Cleansweep? Polygon? G2 Cleansweep? Roundagon? Wavy?

    Check that the brake pads are not grabbing at the rotor "arms."

    If you've completely eliminated the brake itself as the source of the chattering, then it may indeed be the fork. The Judy is not exactly known for being stiff.

    What kind of budget are you looking at for a new fork?

  3. #3
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    XSL_WiLL....the BB7 came with the stock 185 rotor (Avid graphics imprinted). The whole set up is new minus the cable and levers. Will double check the grabbing of the rotor by the caliper but it seems to be lined up perfectly per instructions.

    Fork...somewhere between 150-200. If I dump much more into this hardtail my wife will kick me out of the house!!

    Thanks for the response
    Buellride.

  4. #4
    Meh.
    Reputation: XSL_WiLL's Avatar
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    All of those rotors are Avid rotors. Depending on when the brake was packaged, it came with different rotors.

    Replace those old cables and housing with new stuff. Bulk stuff is fine. Lube up the inside of the housing and the cable. It makes a HUGE difference.

    200 won't buy you anything (good) new, you'll have to look used. What kind of riding do you primarily do?

  5. #5
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    You say that the headset "seems to be" tight. How certain are you? What I'm getting at is, did you actually re-tighten your stem to ensure you've adjusted any play out?

    Even a smallest bit of slop in the headset will manifest itself in an oscillating fork chatter under moderate braking.

    You also say the brake "grabs strong"... are you implying this is too strong for your tastes?

    Two suggestions:

    First, adjust your INboard pad a click or two further away from the rotor to improve your modulation.

    Secondly, adjust your OUTboard pad back however many clicks it takes to cause your pad to engage when the lever is closer to the handlebar, in a more natural position. I personally like my Avids to engage very close to the bar.

    FWIW, some years back, I ran a 185mm Avid on a 1996 Judy with '99 lowers -- at your weight -- and didn't have the chatter problem you describe. I believe the culpret is your headset.
    speedub.nate
    MTBR Hiatus UFN

  6. #6
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    XSL_WiLL...my primary riding is now a mix of trail, small jumps, and road riding. My days of bombing down the trails of the Santa Cruz mountains (back in 1984) are over...

    Speedub...I tighted the stem at the head and short of pulling the forks completely off (which I don't want to do) it seems "tight". The prior set of 160 Shimano's that I replaced never manifested this problem.

    I like a strong brake feel as well as actual gripping/stop. I like your suggestion on the adjustments. I may have to do a better job of "dialing" in the front caliper.....

    In fact upon closer inspection, the rotor flex'es when I apply the brake..seems like I need to relook at my CPS bolts and positioning. Will provide you the results after I adjust and ride this afternoon.

    Thanks in advance for the recommendations.

    Buellride

  7. #7
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    The CPS bolt, 2/3 ~ 1/3 thing is not working out. I read in an earlier post that I should try to just position the caplier by hand and tighten the CPSs....correct?

  8. #8
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    Reputation: Speedub.Nate's Avatar
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    Quote Originally Posted by Buellride
    The CPS bolt, 2/3 ~ 1/3 thing is not working out. I read in an earlier post that I should try to just position the caplier by hand and tighten the CPSs....correct?
    I would recommend forgetting about the whole 2/3 - 1/3 thing, and instead position the caliper so the rotor is nearest to outside pad. More gap on the INboard side gives the rotor more room to flex (which is what it's supposed to do).

    I'd still dial in the red knobs to adjust and hold the caliper where you want it, relative to the rotor, before tightening the CPS bolts.

    Sometimes you're forced to use washers between the fork or frame tabs and the Avid adapter to move the caliper closer to the wheel, if you find that the range of adjustment is not enough to put the caliper where you want it.
    speedub.nate
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  9. #9
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    Thanks Speedub....you validated what I was thinking all along. I adjusted my bike, while here at work, need to hit the trail on the ride home in about 2 hours and I will update the result.

    Thanks again.

    Buellride

  10. #10
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    Just an update to "close" this thread....after manually adjusting the BB7 in relation to the rotor and ignoring, as suggested, the 2/3 and 1/3 instructions. The front brake worked perfectly and the chatter is non-existent on the fork. Confirmed the headset is fine.

    As a note, the rear brake set up fine with the provided instructions. The front brake suffered from rotor flex from the outboard pad (the ONLY one that actually moves under braking). Thus by placing the inboard pad as reasonably close to the rotor as possible (after a few "advancing" clicks with the inboard dial) and mid-point was determined under brake actuation and the CPS bolts were bolted down. Fine tuning eliminated some the rotor rub that occurred...turns out the rotor was very very slightly warped. One click "out" for both pad eliminated the rub.

    Now the front brake grabs and holds like all reviews regarding this great brake!!!

    Thanks for all the help!!

    Buellride
    Don't Like it? Tough...Deal with It.
    Besides...What is the Blast Radius of an EXCUSE?

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