vibration when braking at high speed

[bcadou]

Hello guys

I get vibrations in my braking pedal when braking at high speed, no vibration at regular speeds. Do you know what it can be?

thank you

[Mark A S]

Sounds like slightly warped disc's, you would probably not notice at slower speeds.
Does the brake pedal pulsate?

[bcadou]

yes it does, but only at high speeds.
Do you know what could cause warped discs?

[Mark A S]

Yep, leaning on them too hard

[bcadou]

you mean braking too hard? (sorry, english is not my mother tongue).

I am surprised as I do not remember of braking extremely hard nor very often, I never been on track where I suppose you d brake harder and all the time.

Do you have any other idea in mind? if not, then it must be that, but I though tuscan brakes where especially strong.

[drivingfroggy]

I was told many years ago that sitting in traffic with warm brakes and your foot on the pedal can put hot spots onto the discs and cause warping.

[bcadou]

ouch, that is more likely, as I was stuck in the French traffic jam for a quite while just before this appeared, and it was super hot that day ... :S

[TVR_owner]

bcadou said:

ouch, that is more likely, as I was stuck in the French traffic jam for a quite while just before this appeared, and it was super hot that day ... :S

The heat required to cause problems when foot left resting on brakes (or handbrake on) will not be created by any ambient temperature.

It maybe just cold brakes (expereinced after long high-speed running without use) and aftermarket pads that are too hard.

I'd be very suprised if anyone has actually warped (misnoma) discs during road use on a Toocan.

[977]

I suppose if you were to brake from say, 100mph to 0, and leave your foot hard on the brake, the compression accompanied by the hot pads keeping that section of the disc hot, when the rest of the disc is cooled rapidly by the surrounding air might cause a small discrepency?

[dvs_dave]

Warped discs are in most cases not warped at all. What it is is uneven deposits of brakepad material on the disc. It's this thin layer of material on the disc that actually gives you your braking power. The deposits get un even if the brakes get hot and you come to a stop and don't release the brakes. Excess pad material gets 'burned' onto the disc therby giving the feeling that the disc has warped. All it is is a slightly thicker deposit on that part of the disk.

To fix it, find a quiet stretch of road and brake as hard as possible without locking up from about 60 mph down to walking pace. Don't stop! Steadily accelerate back up to 60 and brake again down to walking pace. Repeat this 10 times. You should be able to smell the brakes by the end which is good.

What this process does is re-lines the discs with a fresh even surface making the judder go away. This certainly worked for me as you're essentially re-bedding the pads and discs.

[FOT Fast]

I managed to warp the disc's on my old SV650(2000) and that was due to the caliper seals going and causing the pistons to become sticky. I later realised that it was mainly due to pressure washing the wheels of the bike far too often!

[bcadou]

Thank you all, I ll try your technique dvs_dave

[Chequred Demon]

I agree with DVS_Dave. It is very unlikely that discs would "warp" under normal road use. Do as he says and all will be well. Mine were fine repeatedly stopping from 150mph+ on a runway for most of the day, though towards the end there was a little vibration. I used the car normally on the way home and the vibration went away.

[bcadou]

thanks mate

I ll try tonight and tomorrow morning, I have a 6k service tomorrow morning with Dom anyway.

[TVR_Tuscan]

I had the exact same problem. Because it varied slightly from trip to trip, I understand the quiet road proposal, but I went for a more "mechanical" solution by having the disks skimmed (a few days ago actually).

Whether deposit or warped, before skimming, they measured 0.1 mm of "unstraightness" on each disk. Got them sand-washed, then straightened.



Maybe a bit drastic, but inexpensive (approx 2 x EUR 60), very efficient and easy to carry through ; wheels off, callipers off (4 bolds), sandwash and skim, callipers back on, wheels back on.

Half an afternoons work, brakes like a BMW again. Almost.