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Trouble with V-Brakes and Suspension Forks

Discussion in 'Bicycle Mechanics and Repairs' started by e-rider, 16 Mar 2008.

  1. e-rider

    e-rider crappy member

    Location:
    South West
    I have noticed that through the travel of the fork, the v-brake changes position in that it pulls more from one side then the other, but this changes as the fork compresses so that the other side then pulls more.

    This leads to brake blocks rubbing when the suspension is active.

    I know I could change to disc brakes but I have a lovely set of lightweight Deore XT Vs.

    It appears that it might be connected to the changing position/length of the brake cable as the forks move.

    Has anyone else noticed a similar problem?
     
  2. punkypossum

    punkypossum Donut Devil

    I have v's and front suspension, but never noticed any rubbing...Surely this should not happen if the fork and the brakes are set up properly?
     
  3. 02GF74

    02GF74 Über Member

    never noticed it and it should not happen if the brake cable is long enough.

    the pother possiblity is that the movment of the fork legs is not equal causing the wheel spindel to twist - the small amount wull be "amplified" by the long ish distance of the wheel diameter at the brake blocks.

    check the sping is not borken, the spindle sits properly in the fork dropouts and the quick release is done up correctly.

    to rule out fork/cable, remove the cable noodle from the brake clip and use a cable tie to set the blocks as they would be if the cable was sitll there.

    repeat what you have done. if you brakes rub, then it is not the cable. obviously your front brkae won't work.
     
  4. 02GF74

    02GF74 Über Member

    oh, and if you want to conver to disc, you need new hubs with cross laced spoking and shifters if yours are one unit items.
     
  5. e-rider

    e-rider crappy member

    Location:
    South West
    I've checked my other two bikes and it doesn't happen with those and they are cheaper set-ups (and heavier --- stronger)

    The forks are brand new Marzocchi MX PRO LOs and the Vs are brand new Deore XTs.

    To state the problem again - when not in use, the brakes are set perfectly with equal pull from each side; the cable is the correct length and everything is fine - yes, the wheel is in the dropout correctly (I've been riding for 20 years!!!)

    As the fork compresses the brakes no longer pull evenly, but when the forks return to the start position everything is fine again.

    I've done some tests and I've noticed that there is some flex in the wheel, and this might imply that one fork legs is exerting more pressure than the other - which is quite possible as they have a coil in one side and air in the other.

    I've also played about with the cable and noticed that as the forks compress the cable moves slightly and this has a small influence on the caliper position - try it; get hlod of the brake cable and move it about as you pull on the lever - it does have an effect!

    I also think that there could be some flex in the fork legs as the bridge doesn't look that strong on these forks.

    The easy solution is to adjust the brake blocks so that there is a good distance between them and the rim, but I like to ride with them pretty close usually.