Brake/Fork Chatter... lube the rim?

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Permalink Reply by Cyclocross Magazine on December 18, 2009 at 8:29pm

we've been trying that too - it does work...tektro, trp and frm make mini v-brakes. we predict they'll make a come back. they don't quite have the power of a well set-up low profile v-brake but are easy to adjust for sure, and effective in dry climates.

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Permalink Reply by G on August 6, 2018 at 12:31am

 I solved this problem recently.  Maybe someone other than me is still running canits.  I have a 61 cm frame, and an all carbon fork.  Very deep from front to back, very stiff looking fork, on a Bianchi cross - specific bike.  Replaced the Kool - Stop v-brake pads that came with the bike, reasonable stopping distance down from 90+ to 45'.  Some squeal, but I'm mostly recreational riding with my wife or alone I tend to use planning, awareness and line-picking to save my a** because I know the brakes won't.  Then I start CX boot camp class.  Start-stop drills, slamming on the brakes from all-out bring out the Irish bainshee wail hidden in my Italian bike... I see the fork judder literally bringing the hub behind the line of the top tube.  My stops are around 30' since I don't dare hit that front brake any harder for fear of shearing off the fork.  I think, I sketch.  I research.  

https://www.velonews.com/2010/09/news/cyclocross/technical-qa-with-...

Zinn confirms my thoughts:  The brake stops the wheel, the tread grips the ground, the frame/rider keep hurtling 

forward.  The fork bends, and on an all carbon fork, even bends where the fork crown meets the steerer... this in turn stretches the cable, clamping the brake more tightly on the rim.  Judder happens because the front tire tears away a little grass, releasing the tension in the system, which is reapplied when the tread bites in again and/ or the forces on the wheel overcome the pressure of pads on rim and slippage occurs, which are reapplied because I still have a death grip on the lever.   

Solution 1) Get a v-brake.  Ok, fine but Paul said their Mini-V with my Campy Ergo would require a very true rim, and I'd have to set the pads very close to get it to work.  Not ideal for cross...

Solution 2) shorten that darn stretched cable.  I find there is such a thing as a "fork mounted brake hanger".  I buy one from the LBS.  As I am doing all this, I realize that the incredibly clever squeegee tip built into the rear edge of my incredibly grippy brake pads is adding to the problem by eliminating at least some of my toe-in, and allowing "catch and release" of my rim.  So...

Solution 3)  I reverse my Kool-Stop v-brake pads to put the squeegee on the trailing edge of the pad, resulting in automatic toe-in.   I will reverse the pads when the rains come home to Seattle.

I tested the bike on level grass, from near golf-course smoothness to bouncy-like-Pachinko crabgrass.  From a roliing start full tilt sprint of 150', slamming on the brakes resulted in No squeal, No judder, and Stop in 15'.  

If you have cantis and carbon forks, go get a fork mounted brake hanger.  I swear on the Constitution, I have never seen 

a single $15 part make so much difference in the performance of a bike.  

BTW - why did I leave those really long, arced v-brake pads on the bike?  Well, I thought more surface friction = faster stopping = a good idea for a 200+ pound rider.  Kind of like having a disc brake on the front. 

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