brake problem

jeff baron said:

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 --- _\\/\-%)
_________(_)`=()___________________(_)= (_)_____

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 hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

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 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 hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

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, 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 hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

You need to localize the exact spot where it is hitting ,then you can see

if

Quoted message said:

it's the rim joint or not. Maybe you can come up with some idea on how to

do

Quoted message said:

that while riding,maybe someone could walk along beside bike while you

apply

Quoted message said:

brake to pinpoint spot where it knocks? Ben fox

"jeff baron" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

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

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 hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

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 baron <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

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