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  1. #1
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    Improving rear brake modulation??

    Hi

    I've recently built up a new singlespeed hardtail bike. I'm continuing to use my Avid BB7 brakes from my previous bike. I've really improved the feel of the front brake on this build, I changed from the 160mm roundagon rotor to the 185mm Cleansweep G3 rotor, and also changed the cables housings to Jagwire Switch. I don't know why this made such a big difference in the way the brakes feel but it did. It is much closer to how my Hope hydros feel on my full suspension bike.

    The rear brake on my singlespeed is still using the roundagon rotor, and the one thing I haven't quite figured out yet is how to make it so that it doesn't lock up so soon. I'm not sure if changing the rotor to a Cleansweep G3 will help in this dept or not. I really wish that there was a 140mm option for the rears on the BB7s like I have for my Hope brakes.

    The Switch cables really reduce that harsh mechanical feel that I've always associated with mechanical disc brakes, I doubt they have much to do with modulation though. I've tried fumbling around with the dial on the Speed Dial 7 levers but that isn't helping much. Part of the problem with that is I haven't found any description of how using that dial effects modulation. I'm just turning it one way or another and riding to see if it gets any better.

    I'm also wondering if it may be just that with the full suspension bike the rear wheel is in better contact with the ground under braking. As the weight transfer goes to the front maybe the rear of the full suspension bike can extend and keep the rear on the ground while the hardtail lifts the rear in the same scenario.

    Any suggestions would be appreciated.

    Thanks, Derek

  2. #2
    PCC
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    I believe that you can mount a 140mm rotor on the rear by using a 160mm front adapter in the rear. I wouldn't do this, though, as you probably can get the brakes to have better modulation while keeping the 160mm rotor.

    The Speeddial levers can be adjusted for more braking power or better modulation. If you turn the adjuster clockwise so that the pivot point is towards the knob you should have better modulation while moving it away from the knob should give you more power. When you set up the BB7 rear brake how did you set up the brake arm linkage? Is it sitting on its rest when the brake lever is released or is the cable tension preventing it from hitting the stop? With the arm sitting on its rest with the brake lever fully released the modulation should be improved. If you loosen the pad adjusters and pull the arm over towards the cable housing before tightening the anchor bolt you are changing the leverage ratio a slight bit which gives you a bit more braking power.

    You are correct that a FS bike helps because the suspension helps to keep the rear tire in contact with the ground which helps to keep the tire from locking up while the hard tail, with the higher unsprung weight, would have a more difficult time keeping the tire in contact with the ground.

  3. #3
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    I have noticed a hugh amount of increased modulation once I sanded my pads. Now, almost two years after a lot of trouble with the BB7s, they work as everybody told me they should.

    I run 185mm front and 160mm rear, both Roundagon.

  4. #4
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    Thanks, I'll try sanding the pads, I hadn't heard of that technique before.

    Quote Originally Posted by daleksic
    I have noticed a hugh amount of increased modulation once I sanded my pads. Now, almost two years after a lot of trouble with the BB7s, they work as everybody told me they should.

    I run 185mm front and 160mm rear, both Roundagon.

  5. #5
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    modulation

    After seeing the video on how to set up Avid BB7,I would just try what they say not to do.IE,Start with the pads dialed out a ways and pull them in with cable adjust.Now you don't have all the leverage.It should take more to lock them up having de-tuned it.

  6. #6
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    do you have a link for this video?

  7. #7
    rebmem rbtm
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  8. #8
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    I just greatly improved my modulation on my BB7s. I'm running 203 front and 185 rear.

    My rear has always been a cleansweep G2. Front is Roundagon. I just installed a cleansweep in place of the roundagon along with Alligator ceramic pads. They had no power at first and all of a sudden, full power after about my 10th hard stop. Modulation was greatly improved over the roundagon and stock pads. I wanted to know if it was the pads or rotor so I installed the set of ceramic pads I originally bought as spares for the front on the rear. Same thing on the rear, no power, wouldn't even lock the rear tire and then bam, full power which is as good or better than the stock pads. I would have to say the pads made a huge difference in modulation. I can no doubt modulate the rear brake much, much better than before. I can easily keep it right at the limit without locking. I'm disappointed I've run the stock pads for this long.

  9. #9
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    That video doesn't have much to do with modulation, just properly installing the brakes.

    However on one of the other threads referenced I finally found a link to the Avid setup pdf for the speed dial levers. Which actually explains which way to move the speed dial knob for more modulation vs power.

    http://sram.com/_media/techdocs/spee...-7-install.pdf

  10. #10
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    When I had BB7s, I improved the modulation by doing the following:
    1. G2 rotors
    2. Speed Dial 7 levers
    3. Teflon coated cable (this really helped the lever return more)
    4. SRAM Flak Jacket FULL cable housing.
    5. I used organics in the front and sintered in the back. Organics seem to have a better feel, but sintered more power.
    Lead by my Lefty............... right down the trail, no brakes.

  11. #11
    Hardbooter
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    Quote Originally Posted by ziscwg
    When I had BB7s, I improved the modulation by doing the following:
    1. G2 rotors
    2. Speed Dial 7 levers
    3. Teflon coated cable (this really helped the lever return more)
    4. SRAM Flak Jacket FULL cable housing.
    5. I used organics in the front and sintered in the back. Organics seem to have a better feel, but sintered more power.
    You want more power in the back? I would prefer the more power brake up front, and more modulation out back.

  12. #12
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    Quote Originally Posted by KingCrimson
    You want more power in the back? I would prefer the more power brake up front, and more modulation out back.
    You do realize you can have both more power and better modulation at the same time, right? It seems like it's assumed on this board that more power= less modulation.

  13. #13
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    Smaller rotor will give you what you're looking for; more force to lock up the rear. Otherwise, you can put a really light rotor on there, with a ton of holes in the brake surface; this will reduce likelihood of locking up too.

  14. #14
    nnn
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    For BB7s I also find adjusting the stationary pad further from the disc increases modulation, 2 or 3 clicks max though, otherwise the rotor deflects too much.
    "Life begins at 140" Richard Burns
    http://www.nikolay-k.com

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