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Fork Chatter! Help!(6 posts)

Fork Chatter! Help!ElvisMerckx
Sep 17, 2003 6:32 AM
I had serious fork chatter problems last year, so this year I changed the rims, brake shoes, and even the headset in the hope of finding a combination that didn't shudder under hard braking. Unfortunately, all the upgrading didn't work.

I'm talking about VIOLENT fork chatter too. The entire front end vibrates like a jackhammer, making downhill braking difficult and downhill turns impossible.

Current setup: aluminum fork, Spooky brakes, Ritchey pads, aluminum rims.

What can I do?
What brand fork are you using?....SS_MB-7
Sep 17, 2003 7:00 AM
The first obvious place to check is your headset...make sure it is tight, but not too tight. Is the lower headset race properly seated on the fork's crown? Are the headset cups fully inserted into the frame?

Also, are you using ceramic rims?

It sounds like the combination of rim, brake, brake pads, tire, terrain and fork is not good. Does it chatter all of the time or under certain conditions? If the latter, what conditions seem to bring-on the chatter.

What brand fork are you using? Have you tried another fork?

Ride Hard,
Mike B.
http://www.geocities.com/one_speed_MB
Redline -- stock fork . . .ElvisMerckx
Sep 17, 2003 7:13 AM
. . . and conditions don't matter. It chatters when wet, dry, cold, warm. The chatter gets worse on downhills and/or when braking hard.

I've tried ceramic and aluminum rims, 2 types of brakes, 4 types of brake pads. The headset is not lose.

This seems to be more of a combination of my height, weight, frame geometry, and a flexible fork.
re: Fork Chatter! Help!triangleforge
Sep 17, 2003 7:30 AM
First place to try is toeing the brake shoes -- I've got a similar set up, but with a fairly flexy Columbus steel fork (which I really like) so fork "chatter" can be a real issue under hard braking. With sufficient toe-in, the problem goes away and I get good, modulated braking. A teammate of mine had exactly the same problem a couple of weeks ago (with Avid brakes on an Alu fork), and a quick check of his toe-in cured it immediately.

As you've doubtless discovered, the Spookys aren't easy to set the toe in on, as you actually have to bend the brake body to do it. The best trick I've found is to remove the shoe from the brake and insert a phillips screwdriver of about the same diameter as the post (phillips only because the blade isn't wider than the shaft) and use that as a lever to bend the body. Bend a little, insert the brake shoe, check your work, repeat as necessary. It's a pain, but it does make a difference. I've heard of folks using channellocks on the Spooky, Empella and old Mafac brakes to do the same thing, but I'm not really clear on how & where you grab the brake with the pliers. I've also heard of people using a flat file to shape the shoe to achieve toe-in, but that sounds like even more of a pain than the way I do it.

Another thing that can help is to clean the brake shoes & rims -- I'll periodically clean them with a strong Simple Green solution and a toothbrush, then rinse well, same with the rims -- on occasion, though, I've had this make the shoes even more grabby than usual until the rim & pad get back on terms. There's no pattern to it that I can discern, sometimes it happens, sometimes not, and when it does I've just got to be careful for the first 3-5 stops.

Good luck!
I think you've got it!ElvisMerckx
Sep 17, 2003 7:48 AM
The brakes are toed somewhat. But only to about the same angle as my road brakes, but given the longer, softer brake pads on my cross rig, I should probably tweak the angle a bit further. One would think the Ritchey pads probably flatten against the rim sooner than my road pads, and, under heavy braking they start toe-ing backward. I'm banging my head on the keyboard for not thinking of this myself . . . and sooner (coulda' prevented several dramatic wipeouts last season)!

I'll try this tonight and let you know how it works out. Thanks!

Also, great advice on the screwdriver!
I think you've got it!dlbcx
Sep 17, 2003 8:03 AM
Another possibility is to sand the pads at an angle. This is what a teammate does for his brakes (Spookys). He didn't want to bend the brakes so he took off the pads then used a bench sander to put a chamfer in the pads.