brake problem

Discussion in 'Recumbent bicycles' started by Jeff Baron, Jan 26, 2003.

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  1. Jeff Baron

    Jeff Baron Guest

    much appreciate some advice on dealing with a braking problem on my
    vivo. installed magura brakes. bike is used but only has a couple hundred miles on it. sun rims.
    braking on real wheel smooth. but on front wheel, as i increase pressure on brake levers to
    stop bike, feel a strong knocking that starts with the wheel and shoots up the handlebars.
    stronger the pressure on the lever, stronger the knocking. seems one wheel revolution
    produces one jolt. rim seems true, and when i rub my finger over the rim, seems smooth.
    advice on a fix much appreciated, thanks, jeff baron
     
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  2. John Foltz

    John Foltz Guest

    jeff baron wrote:
    > much appreciate some advice on dealing with a braking problem on my vivo. installed magura
    > brakes. bike is used but only has a couple hundred miles on it. sun rims. braking on real
    > wheel smooth. but on front wheel, as i increase pressure on brake levers to stop bike, feel a
    > strong knocking that starts with the wheel and shoots up the handlebars. stronger the pressure
    > on the lever, stronger the knocking. seems one wheel revolution produces one jolt. rim seems
    > true, and when i rub my finger over the rim, seems smooth. advice on a fix much appreciated,
    > thanks, jeff baron
    >
    You may be feeling a misaligned rim joint. They're not always smooth where the mfg joins the two
    ends to make a circle. If that's it, you can minimize the problem by sanding or grinding the high
    spot. If the joint is actually loose, the rim will have to be replace - quickly!
    --

    John Foltz --- O _ Baron --- _O _ V-Rex 24/63 --- _\\/\-%)
    _________(_)`=()___________________(_)= (_)_____
     
  3. Jeff - I think John F. is right. Sounds as though there is an uneven rim weld. It is unlikely that
    you will be able to realign trhe joint, though the lbs has a tool for that task. The problem
    twofold. One, the rim is compromised. Second, is that the front pads heat very fast and get grabby
    (before becoming completely ineffective) , compromising braking and steering. You need to fix or
    replace the rim quickly. I had this problem with my new VRex, and eventually went through 2 OEM rims
    before RANS replaced the front with a Sun Rhyno lyte welded rim. No problems since. Jon Shinefeld

    "jeff baron" <[email protected]> wrote in message news:[email protected]...
    > much appreciate some advice on dealing with a braking problem on my
    > vivo. installed magura brakes. bike is used but only has a couple hundred miles on it. sun rims.
    > braking on real wheel smooth. but on front wheel, as i increase pressure on brake levers to
    > stop bike, feel a strong knocking that starts with the wheel and shoots up the handlebars.
    > stronger the pressure on the lever, stronger the knocking. seems one wheel revolution
    > produces one jolt. rim seems true, and when i rub my finger over the rim, seems smooth.
    > advice on a fix much appreciated, thanks, jeff baron
     
  4. Ben Fox

    Ben Fox Guest

    You need to localize the exact spot where it is hitting ,then you can see if it's the rim joint or
    not. Maybe you can come up with some idea on how to do that while riding,maybe someone could walk
    along beside bike while you apply brake to pinpoint spot where it knocks? Ben fox

    "jeff baron" <[email protected]> wrote in message news:[email protected]...
    > much appreciate some advice on dealing with a braking problem on my
    > vivo. installed magura brakes. bike is used but only has a couple hundred miles on it. sun rims.
    > braking on real wheel smooth. but on front wheel, as i increase pressure on brake levers to
    > stop bike, feel a strong knocking that starts with the wheel and shoots up the handlebars.
    > stronger the pressure on the lever, stronger the knocking. seems one wheel revolution
    > produces one jolt. rim seems true, and when i rub my finger over the rim, seems smooth.
    > advice on a fix much appreciated, thanks, jeff baron
     
  5. Daven

    Daven Guest

    Jeff, It may well be the the rim joint. However, I also had identical symptoms that turned out to be
    a very slight bulge on the rim that was not near the joint. I couldn't feel it with my fingers, but
    a pair of outside calipers would stick at that point. A few very careful whacks with a rubber mallet
    took care of it. Dave

    "Ben Fox" <[email protected]> wrote in message news:[email protected]...
    > You need to localize the exact spot where it is hitting ,then you can see
    if
    > it's the rim joint or not. Maybe you can come up with some idea on how to
    do
    > that while riding,maybe someone could walk along beside bike while you
    apply
    > brake to pinpoint spot where it knocks? Ben fox
    >
    > "jeff baron" <[email protected]> wrote in message news:[email protected]...
    > > much appreciate some advice on dealing with a braking problem on my
    > > vivo. installed magura brakes. bike is used but only has a couple hundred miles on it. sun
    > > rims. braking on real wheel smooth. but on front wheel, as i increase pressure on brake
    > > levers to stop bike, feel a strong knocking that starts with the wheel and shoots up the
    > > handlebars. stronger the pressure on the lever, stronger the knocking. seems one wheel
    > > revolution produces one jolt. rim seems true, and when i rub my finger over the rim,
    > > seems smooth. advice on a fix much appreciated, thanks, jeff baron
    >
     
  6. Maybe (one of) the pad(s) just nees to be moved up or down a bit. The bulge may not extent all the
    way from top to bottom.

    Torben

    "jeff baron" <[email protected]> wrote in message news:[email protected]...
    > much appreciate some advice on dealing with a braking problem on my
    > vivo. installed magura brakes. bike is used but only has a couple hundred miles on it. sun rims.
    > braking on real wheel smooth. but on front wheel, as i increase pressure on brake levers to
    > stop bike, feel a strong knocking that starts with the wheel and shoots up the handlebars.
    > stronger the pressure on the lever, stronger the knocking. seems one wheel revolution
    > produces one jolt. rim seems true, and when i rub my finger over the rim, seems smooth.
    > advice on a fix much appreciated, thanks, jeff baron
     
  7. Jeff Wills

    Jeff Wills Guest

    jeff baron <[email protected]> wrote in message news:<[email protected]>...
    > much appreciate some advice on dealing with a braking problem on my
    > vivo. installed magura brakes. bike is used but only has a couple hundred miles on it. sun rims.
    > braking on real wheel smooth. but on front wheel, as i increase pressure on brake levers to
    > stop bike, feel a strong knocking that starts with the wheel and shoots up the handlebars.
    > stronger the pressure on the lever, stronger the knocking. seems one wheel revolution
    > produces one jolt. rim seems true, and when i rub my finger over the rim, seems smooth.
    > advice on a fix much appreciated, thanks, jeff baron

    Jeff-

    Since the rim seems smooth, there's a spot where the friction is greater than the rest of the rim.
    Clean the rim with a Scotchbrite pad or steel wool to remove all the old brake pad residue.

    If that doesn't work, carefully clamp a couple pieces of 600 grit sandpaper between the pads and the
    rim. Ride up and down the block a couple times, lightly clamping on the brakes. This should smooth
    out the brake track somewhat.

    Also, since you're feeling a "strong knocking", double-check the headset adjustment. A slightly
    loose headset can amplify the "grabbing" to an enormous degree. I've got an upright with a divot in
    the rim (I smoothed the rim joint *too* much) and it's nearly unrideable with a loose headset.

    Jeff Wills
     
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