Wednesday, October 7, 2009

Brake Chatter/Judder: A Formidable Foe

Sometimes riding bikes with less than cutting edge technology provides opportunities to chuckle about the problems others face with their fancy schmancy equipment. I'm using an early 1990s Pinarello for my 'cross riding and racing, and its a pretty darn good steed. Sure, its not built for me, or anybody else with size 46 feet. Yes, toe overlap sucks. But its the bike I have, it has a lot of character, and its orange. It also does not suffer from brake chatter.

I only started hearing about brake chatter a few years ago. It seemed like the combination of cantilever brakes and 'cross forks was all of the sudden creating havoc. People would pull their brakes and the front wheel would lurch back and forth, skipping off the ground. It was nuts. As a mechanic, I looked to the typical potential causes: rim irregularities, loose headsets, brake pad adjustment, brake pad compounds and cable geometry. No one change seemed to sufficiently solve the problem. Carbon forks were usually the spec, though I have seen it on a few good quality steel forks. I started to do some online research last year.

Since my own personal bike does not suffer from chatter, nor does my Cross Check beater, and I'm not working in the shop these days, I had no opportunity to try the theory I settled on. The theory is that the chatter is caused by irregular tension on the brake cable between cable hanger and straddle as the fork flexes back and forth. The proposed solution: mount a cable hanger to the fork. Kinesis has just come out with a carbon 'cross fork that includes such a hanger for this purpose. Today I cam across a blog post that further details this problem and proposed solution, and it appears it works well. Check it out. If anyone knows of such hangers that don't look like cheap crap, let me know. Brake chatter be gone.

7 comments:

Rob Young said...

Congrats on the good rankings in the madison!

I think that fork shudder can occur for a great number of reasons. I've also thought more cross forks should have an integrated hanger. I love the cantilever brakes on my touring bike, but feel the tight fitting hanger gives me headaches.

When I built my cross bike, I decided to try v brakes and tektro v brake drop bar levers, to see what the fuss was about them. I've been quite happy with them, it's a solid setup.

The tektro brake cable housing stop is great, what a good idea.

Matt Surch said...

Thanks Rob!

You are certainly right, there are many reasons forks shudder. The fork mounted cable hanger move will likely be the last ditch effort many make after combating the problem for some time.

I like v-brakes, having used them for years on the mtb. In fact, I got a pair of the XT brakes the minute they were released...and they cost a fortune! Unfortunately, v-brakes have less clearance to the tire than cantis. We don't have much mud here, but in other locales racers deal with massive amounts of it, with grass mixed in. I bet many of us here could get away with v-brakes just fine. We'd have to use cable cams to produce the adequate pull with our integrated shifter/brake levers though. It seems simple to either run a fork that does not flex a tonne or take the steps discussed above to sort it out.

Simon Smith said...

I posted my solution to Cyclocross Ontario's site....the fork mounted hanger worked for me.
Fork chatter - Cyclocross Ontario

Matt Boulanger said...

Hi there- I wrote the post you linked to- and i should give credit to Nippleworks for the cable hanger idea. I should also point out that the cable hanger only works to limit chatter if everything else is set up properly. Mostly, I found that I had to toe my pads way in, and the combination of well-adjusted pads and hanger has stood up well. Cheers, Matt.

Rob Young said...

Yeah, lever pull is the big issue with road levers/v brakes for sure. I'm not sure I agree with you about mud clearance though. While canti's would have greater mud clearance than my V's; my V's extend above the bottom of my fork crown, they have pretty good mud clearance.

I think a big reason you don't see many v brakes on cross bikes is that canti's work quite well, and the compatibility problems you run into with V's/standard pull road levers make it kind of annoying to attempt.

I really would like to upgrade to SD7's on my cross bike. I have them on my mtb, they're wonderful. The cheapo V's I have on my cross bike work so disturbingly well though, upgrading doesn't make a lot of sense.

Matt Surch said...

True Rob, I do see v-brakes appearing on the odd cross bike since the cable is higher than the crown anyway. One of our local fast guys, Nathan Underwood, is running a v on the front and a canti on the rear of his Colnago. Apparently some of them work ok without a cam, since the arms are shorter than the mtb versions.

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