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Violent Vibrations with my front brake

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Violent Vibrations with my front brake

Old 12-11-10, 07:27 PM
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rnt654
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Violent Vibrations with my front brake

I have an early 90's Specialized Crossroads Hybrid bike. when I try and stop my front brake shakes and vibrates pretty violently. It's the only way I could describe it. Sometimes it get a loud squeaky noise from the front brake when I stop. Not sure what's causing it. Is it the Wheel, Brakes, Front forks or a loose headset. Any advice would help Thanks

also it's a 700c wheel and cantilever brakes

Last edited by rnt654; 12-11-10 at 07:33 PM.
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Old 12-11-10, 07:55 PM
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HillRider
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This topic has come up several times in the recent past. I assume your front brake cable housing stop is mounted on the top of your headset or even on your stem, correct?

The explanation seems to be that flexing of the steerer tube under braking load alters the tension in the span of brake cable between the housing stop and the straddle cable causing vibration and varying brake force. Larger frame bikes (long steerer tubes) and bikes with carbon steerers and/or carbon fork blades seem most prone to this. Small frames with 1-1/8" steel steerers are less likely to be affected but it can happen to any type.

The easiest "cure" is to mount the cable stop on the fork crown using the hole intended for a fender bracket. Here is one source of these mounting brackets:

https://www.amazon.com/Tektro-Brake-H...0&sr=1-2-spell

Lennard Zinn had a major article on this problem in the Tech section of the VeloNews web site a few weeks ago. Here is one article:

https://velonews.competitor.com/2010/...shudder_147730
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Old 12-11-10, 08:02 PM
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surreal
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could be a number of things. try the following; i'm trying to put them in order, but you might want to try things in different order.

-before you even get started, make sure the front wheel is tightened down in the fork, and make sure that the brakes are firmly tightened down in the cant bosses.
-make sure the pads are properly toed-in. This means that the front end of the pads will be ever so slightly closer to the rim's braking surface than the rear end.
-While checking this, also make sure that the pads are properly adjusted to hit the rim's braking surface and only the rims braking surface. I'm assuming these are cantilever brakes; you may need to adjust the spring tension screws on each arm to ensure that the rim is centered between the pads, and that the arms engage and disengage evenly and adequately. There are many resources online that will give you a step-by-step of this process (which may not be necessary anyway. Continue looking into other factors before you do any serious tinkering with your brakes, other than pad alignment.)
-also, make sure that your pads are fresh, and not hard, glazed, cracked, or otherwise $h!tty. If they're not so nice, get new ones. You'll want to replace old pads even if they aren't the cause of your current problem. Many, myself included, recommend kool stop salmon or dual-compound pads.
- When you feel that your brakes are set up reasonably well, squeeze the front lever firmly while holding the handlebar with both hands. Rock the bike back and forth, and make sure that there is no play in the headset. If there is, look into step-by-steps for adjusting a headset, or take it to the lbs if you lack tools/confidence.
-if your fork is a suspension fork, and it's 20 years old, or is otherwise compromised from being worn out or janky from day one, it may be the culprit. The fork is essentially tightened down by proper headset adjustment; any fork-related looseness or similar will likely result from trouble in the fork's inners, or a crack somewhere on the fork. Replace instead of repair in these cases, i'd wager.
-some folks swear that headset-spacer mounted cable hangers cause weird jittering with cantilevers. I have never experienced this, but i've read about it enough online to believe in it. V-brakes are one obvious remedy for that kind of thing, but you'd need to replace the lever(s) as well as the brake unit. Not worth it, imho. If nothing else is working to alleviate your problem, you may want to look into a fork-mounted cable hanger, or playing around with the order and tightness of your headset spacers.

As far as i can tell, that about covers everything. I hope someone else can cover anything i'd missed.

Good luck!
-rob

ps- Seems like Hillrider was posting a response while I was composing my somewhat lengthy one. The gadget he linked you to is the fork-mounted hanger that I'd referred to above.

Last edited by surreal; 12-11-10 at 08:03 PM. Reason: post-script mayhem
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Old 12-11-10, 08:07 PM
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mt645: I've put the Specialized Tricross Fork Brake hanger https://www.specialized.com/us/en/bc/...jsp?spid=47409 on two bikes (one MTB and one hybrid) recently and been very satisfied with the results. Unlike the Tektro model it has an additional barrel adjuster which you might find convenient. It comes with hardware for both alloy and carbon forks.
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Old 12-11-10, 09:10 PM
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rnt654
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Thanks for the help.
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Old 12-14-10, 07:37 AM
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Surreal wrote a great sequence of steps to try.
The only thing I'd add to it is to make sure the bolt which olds the caliper to the fork is adjusted properly (not too loose).
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Old 12-14-10, 01:23 PM
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Had a similar problem on a 1998 hybrid I recently picked up. Even though the brake pads looked fine, I changed them out. Immediately the problem went away.

New pads will not be the solution every time, but they can be the solution.

If you do replace the pads, make sure the toe in is correct.
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Old 12-14-10, 01:43 PM
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Did you Toe in the brake pads already??
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Old 03-17-11, 04:02 PM
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Looks like I didn't need the cable stop. just a few adjustments to the brakes, stem and head set worked
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