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Massive brake problems(10 posts)

Massive brake problemsJan Gerrit Klok = "TUFO-man"
Sep 14, 2001 11:22 PM
On both my cross bikes, with totally different rims (carbon and alu), forks (steel and alu), brakes (Spooky's and Shorty 4)and pads, I have the problem of resonation or whatever it's called. I can see the fork flex 1-2 inches, very fast. The pads seems to be locking and slipping at very high frequency, almost throwing me off the bike!
And this is just on the road, for in the mud, obviously my front wheel really locks and I have big problem staying on.

Can someone tell me how I should set up the pads on my canti fronts? Let the front of the pad touch the rim front, the other way round, or perhaps touch evenly?

THANKS!!!
re: Massive brake problemsBAM
Sep 15, 2001 5:00 AM
Typically the front of the pad touches first, but sometimes you need to have one pad touch heel first with the other touching front first. You can also have both pads touch heel first, but try having only one pad reversed first. Having both pads reversed can reduce the braking performance. What your describing was fairly common before MTB suspension forks came out. This was partically true of light weight steel (higher end forks) and almost aways the way with aluminum. You will need to see what works in your situation. First try reversing one pad if that fails then put it back to normal and reverse the other. If all else fails try reversing both.
re: Massive brake problemsJan Gerrit Klok = "TUFO-man"
Sep 15, 2001 7:27 AM
Thanks! I'll give that a try.
re: Massive brake problemsPeter Kupferman
Sep 15, 2001 10:54 AM
I have the same problem with my Ritchey Swisscross with Avid 4s. I think the fork flex is good and accounts for its great shock absorption-but the brakes howl and sequeal. I've tried all the usual stuff of changing rims, toe-in, out,and flat and have given up! Extreme toe-in has eliminated the sound, but the brakes are mushy. Wish I could get discs.
re: Massive brake problemsBAM
Sep 15, 2001 2:40 PM
Have you tried a brake booster or changing to different brake pads such Shimano XTR pads?
re: Massive brake problemsPeter Kupferman
Sep 16, 2001 6:09 AM
I've tried many different pads. I think a brake booster would be good to try-but even if it worked, it wouldn't look like a cross bike anymore!
Mechanical advantageBipedZed
Sep 17, 2001 6:50 AM
Without seeing the specifics of your setup, I would venture a guess that your cantilever setup (mechanical advantage) is overpowering the fork causing flex. You must find the optimal mechanical advantage (adjusting the height of the cable yoke) for your application. Pad toe-in reduces squeal, but will not affect the flexing you are experiencing.

Check out the following articles on cantilever adjustment and mechanical advantage:
http://www.sheldonbrown.com/cantilever-geometry.html#mechanical
http://www.sheldonbrown.com/cantilever-adjustment.html
Mechanical advantageJan Gerrit Klok
Sep 17, 2001 7:43 AM
One of my bikes has a Shorty4 setup. I cannot vary the cable height, because if the little cablepipe that the 4´s use. I could shorten it, but not make it longer.
And since when is there such a thing as over-powering with brakes? I am not at all happy with the power I´m getting out of them. Maybe I´m spoiled with my V´s on mtb´s...
vibration - similar problem?Pablo
Sep 17, 2001 7:57 AM
I'm the world's worst bike mechanic so forgive me if this is a dumb question. Yesterday I adjusted the toe-in on my rear pads (Shorty 4's on LeMond Poprad) to remedy LOUD squealing. The squeal is gone, and the braking feels fine in terms of power, but under moderate + braking, I get a fairly high-frequency vibration that even comes up through the seat and is uncomfortable - although some riders may consider this a plus:).

I guess readjustment may be needed, but is this a problem that needs a brake booster?

Thanks!
re: Massive brake problemsflyweight
Sep 20, 2001 8:37 AM
I had Avids on one of my bikes and have had the exact same problem on several bikes with several different brakes. The first thing I did was loose the cable hanger than came with the bike. Get an old school DiaCompe or Mafac straddle cable hanger. Set the calb hanger pretty high up, higher than the 90 degree angle usually recommended. Look at some of the pictures of pro racers in Europe and you'll see the straddle cable hanger is sometimes half-way up the head tube. You'll have to tinker with the height before you find the sweet spot.

Overall the Avids didn't impress me. I think they might be too stiff. I've noticed that the best cross brakes tend to be either low profile (Deore XT, Paul Neo Retro low profile) designs or fairly flexible (Mafac, Empella) I've had the most chatter/vibration problems from stiff, wide arm designs (Paul and Avid) I'm starting to think that the stiffness of the brakes overpowers the flexible fork blades and sometimes the chainstays.