Front fork shudder / brake grab

Hi All,

I took my road bike out for its maiden voyage last night. The front
brakes were grabbing and causing the front fork to shudder terribly.
Basically unusable. The set-up is a Surly crosscheck frame and fork,
Avid SD-5 brake (linear pull), Dia Compe 287V lever, Kool Stop salmon
pads (used), Velocity Dyad rim.

I did a newsgroup search and came up with some things to check out:

- ensure rim is true, especially the vertical trueness
- clean rim
- check pad angle
- check for play in calipers
- check headset (already ruled out)
- new pads
- different wheel


I'll try these things when I go home tonight, but from what I've read
these problems can be hard to fix. Any other advice or suggestions
would be appreciated.

Regards,
Anthony

On Wed, 9 Apr 2008 16:30:28 -0700 (PDT), Anthony DeLorenzo wrote:

Hi All,

I took my road bike out for its maiden voyage last night. The front
brakes were grabbing and causing the front fork to shudder terribly.
Basically unusable. The set-up is a Surly crosscheck frame and fork,
Avid SD-5 brake (linear pull), Dia Compe 287V lever, Kool Stop salmon
pads (used), Velocity Dyad rim.

I did a newsgroup search and came up with some things to check out:

- ensure rim is true, especially the vertical trueness
- clean rim
- check pad angle
- check for play in calipers
- check headset (already ruled out)
- new pads
- different wheel


I'll try these things when I go home tonight, but from what I've read
these problems can be hard to fix. Any other advice or suggestions
would be appreciated.


Also check that the brake mounting bolt is tight - it's a beginner thing,
but some people (like jim beam) do miss it.

On Apr 9, 6:30*pm, Anthony DeLorenzo
wrote:
Hi All,

I took my road bike out for its maiden voyage last night. The front
brakes were grabbing and causing the front fork to shudder terribly.
Basically unusable. The set-up is a Surly crosscheck frame and fork,
Avid SD-5 brake (linear pull), Dia Compe 287V lever, Kool Stop salmon
pads (used), Velocity Dyad rim.

I did a newsgroup search and came up with some things to check out:

- ensure rim is true, especially the vertical trueness
- clean rim

rim AND pad. I like to sand or even use a wee box plane on used pads
to refresh them.

- check pad angle

Crucial to have proper toe in, especially with Kool stops! Proper toe
in makes LP brakes much less grabby. Again, Kool Stops are really
fussy about this.

- check for play in calipers

Grease posts, install brake, torque down mounting bolts, and start
with return spring screws turned all the way in, balance arms by
loosening one or the other--this will give you better feel at the
lever.

On Apr 9, 7:34*pm, landotter wrote:
On Apr 9, 6:30*pm, Anthony DeLorenzo
wrote:

Hi All,

I took my road bike out for its maiden voyage last night. The front
brakes were grabbing and causing the front fork to shudder terribly.
Basically unusable. The set-up is a Surly crosscheck frame and fork,
Avid SD-5 brake (linear pull), Dia Compe 287V lever, Kool Stop salmon
pads (used), Velocity Dyad rim.

I did a newsgroup search and came up with some things to check out:

- ensure rim is true, especially the vertical trueness
- clean rim

rim AND pad. I like to sand or even use a wee box plane on used pads
to refresh them.

- check pad angle

Crucial to have proper toe in, especially with Kool stops! Proper toe
in makes LP brakes much less grabby. Again, Kool Stops are really
fussy about this.

- check for play in calipers

Grease posts, install brake, torque down mounting bolts, and start
with return spring screws turned all the way in, balance arms by
loosening one or the other--this will give you better feel at the
lever.

you say you ruled out the headset, how did you check to rule it out ?
(or you are saying you are knowledgeable enough to be certain it is
fine )

On Apr 9, 6:30*pm, Anthony DeLorenzo
wrote:
Hi All,

I took my road bike out for its maiden voyage last night. The front
brakes were grabbing and causing the front fork to shudder terribly.
Basically unusable. The set-up is a Surly crosscheck frame and fork,
Avid SD-5 brake (linear pull), Dia Compe 287V lever, Kool Stop salmon
pads (used), Velocity Dyad rim.

I did a newsgroup search and came up with some things to check out:

- ensure rim is true, especially the vertical trueness
- clean rim
- check pad angle
- check for play in calipers
- check headset (already ruled out)
- new pads
- different wheel

I'll try these things when I go home tonight, but from what I've read
these problems can be hard to fix. Any other advice or suggestions
would be appreciated.

Regards,
Anthony

Sure fix: stop the front brake housing at the bottom of the steerer
tube (on the fork crown), not the top (in the headset). Redline bikes
come with an aluminum bolt-on housing stop for this.

This mod removes most of the steerer tube's contribution to the flex
in the system in response to braking.

After stuff has worn in (brake pads, rim, etc.) you might not need the
lower housing stop position any more, but when stuff's new and picky
it makes a big difference.

"Anthony DeLorenzo" wrote:
(Item 3) check pad angle (clip)
^^^^^^^^^^^^^^^^^^^
Not hard to check. Not hard to fix. Very likely to help.

Thanks to all for the responses so far. I double-checked everything to
do with the calipers, pads, and wheel trueness. I was able to reduce
the problem but not eliminate it.

I did notice that the brakes are consistently grabbing at one specific
section of the rim. I can't see any difference in the rim itself that
would cause this. I didn't have this problem when the wheel was
mounted on my mountain bike, but the stiffer fork may have just
absorbed it better.

I'm going to try a wheel swap tonight and see if it eliminates the
problem.

On Apr 9, 9:05 pm, "
wrote:
Sure fix: stop the front brake housing at the bottom of the steerer
tube (on the fork crown), not the top (in the headset). Redline bikes
come with an aluminum bolt-on housing stop for this.

This mod removes most of the steerer tube's contribution to the flex
in the system in response to braking.

I second this approach, assuming the simpler changes don't fix the
problem. I'm a big fat guy with a 60cm Surly Long Haul Trucker and a
58cm Bianchi San Jose. The LHT has always been solid as a rock, but
the SJ had terrifying fork shudder until I moved the stop down to the
fork crown; now it's cured completely.

I guess I am a bit surprised to hear that your CC fork suffers from
this. I was actually considering replacing the SJ fork with an LHT
fork at some point precisely because my LHT seems so sturdy. The CC
and LHT fork specs don't look that much different.

On Apr 10, 9:19 pm, wrote:

I guess I am a bit surprised to hear that your CC fork suffers from
this. I was actually considering replacing the SJ fork with an LHT
fork at some point precisely because my LHT seems so sturdy. The CC
and LHT fork specs don't look that much different.

A few factors probably contribute. I am 6'6" 250 lb., riding a 62 cm
frame with a long head tube and steerer, and the linear-pull (V-brake)
is a lot of brake power for a road fork.

I'm more convinced that the problem is the rim. Even when I just
lightly apply the brakes and turn the wheel on the bike stand, it
noticeably grabs in the same spot every time. LBS has one of those
Mavic rim erasers, I'm going to borrow it and see if it helps.

It could just be some initial wear-in issues as well. With tinkering
and riding the problem has improved, at least to the point where the
front brake is now quite usable, although still annoying.

On Apr 10, 9:19 pm, wrote:

I second this approach, assuming the simpler changes don't fix the
problem.

stopping the cable in a different spot, as suggested by a couple
of people (much appreciated!): It's a linear-pull brake, so the
housing runs straight from the handlebar to the brake noodle. No stops
involved. Unless I'm not understanding what you propose.