Brake vibration

[SteveP]

My R300 has recently developed an unnerving brake vibration, presumably on the fronts, when you gently apply the brake leading to steering wheel wobble. This sensation disappears if you brake harder.

 

In my experience on other cars, this has usually meant warped disks, but can't believe that after just 1600 road miles and two sprints, the disks are shot - AP big brake setup should be able to withstand that.

 

Anything I can easily check to verify this? Or is there something else that might be wrong / caused this.

 

Thanks

 

 

 

SteveP

[Graham Perry]

Check calipers are tight and that front wheel bearings don't have too much play (they should have a tiny amount, that disappears when you spin the wheel)

[Peter Carmichael]

There is a very good explanation somewhere in the archives that "warped disks" are a myth and never actually happen.

 

What does happen is that during bedding in, pad material transfers to form a thin layer on the disk. If this happens unevenly then you get brake judder. The best bet is to dress the disks with garnet (specifically not an aluminium oxide based paper as this will compromise the disk) paper to remove the established brake pad material film and then re bed-in the pads. This is 99% likely to cure the problem.

 

Edited by - Peter Carmichael on 27 May 2003 15:02:54

[Mr Locust]

My roadsport has the same 10" vented front brakes (new type) and there is a tendency for slight vibration when cold and braking lightly. Not really enough to feed back through the pedal though. Disappears when warmed through a bit.

 

Two things;

 

1. It seems to have got less the more I have used it.

2. I try and make a concious effort not to wash the car and put it away with 'wet' on the brakes even if it means going round the block and using the brakes a bit.

 

Cat mids were specifically asked to look at this on PBC and found nothing. Similarly I checked it over and found nothing.

 

Give them a good dose of using....... 😬

 

Peter - you posted at the same time as me. I might just look into that........hmm.

 

Edited by - Mr Locust on 27 May 2003 12:08:21

[charlie_pank]

I'd like to second Peter's suggestion. Garnet paper (available from model shops) is the recommended abrasive paper (not sandpaper as the silicon reacts with the disc). I had an awful lot of judder on the front right, it was all sort of skiddy and squealy on very low speed breaking. All fixed with a 5 minute rub-down with Garnet paper.

 

 

 

 

Charlie'n'Kermit

The plan is: Leave for Le Mans on the 7th

S5EVN

[Stuart Faulds]

I'm struggling with the concept that warped disks are merely a myth. Having put disks I suspected were warped in a lathe, there was a discernable 'warp' which certainly wouldn't be accounted for by brake material.

 

Stuart

[Peter Carmichael]

I just report it like I read it...

 

Click here

[charlie_pank]

PC - quite right. The unevenness isn't warping, but "stuff" on the disc trying to turn into cementite!

 

Charlie'n'Kermit

The plan is: Leave for Le Mans on the 7th

S5EVN

[Stuart Faulds]

Peter, thanks for the link. I think 'figure 2' on that page shows what I think of as a warped disk, only the disk hasn't gone into a true cone (ie, some parts of the disk have distorted more than others). Carroll Smith seems to imply that his vision of a warped disk is one which has grown thicker in some places than others, and as such I'm not surprised he's never seen it happen!

 

Charlie, you're more than welcome to come round and try and true this disk up with a bit of Garnet paper, but you'll need a hell of a lot of it, and some damn strong forearms! Your issue may have been caused by pad material on the disk, but it is not the same for every case.

 

Stuart

[charlie_pank]

Stuart,

 

"With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history

 

- I have never seen a warped brake disc"

 

perhaps one of the above is true in your case?

 

 

Charlie'n'Kermit

The plan is: Leave for Le Mans on the 7th

S5EVN

[Stuart Faulds]

It's quite possible that it wasn't correctly fitted since it was done by Caterham and I merely checked the torque rather than stripping the assembly and rebuilding it. Regardless, you're not going to sort it with Garnet paper, and it's quite conceivable that Steve P has a similar problem.

 

Anyway, I feel you're missing my point - I think what I would call a warped disk (disk still a uniform thickness but no longer true) differs to what Smith calls a warped disk.

 

Stuart

[Bare]

Some things ARE different in reality than in Theory. Personally I've seen dozens of Truly "warped" disks over the years. Warped in the sense that the Damned things developed a 'wobble'.. instantly and indisputably evident when mounted onto the Disk Turning Lathe.

Interestingly, Solid as in non vented Rotors, seem to suffer from this far less than than their Vented cousins... Bigger discs also seem more suseptible.

From personal experience I've also learned to my disgust that it V easy to "warp" a Rotor.. just over heat 'em and then keep your foot firmly on the brake pedal waiting for a Stoplight.

If Memory serves AP had (has?) a V informative and Educational treatise on exactly how not to do this.. and it's Current.

[DC]

Just read the thread, and strangely enough my R300 has the same problem, which has only just started to happen (1300 miles). Gentle braking gives a feeling of on off on off, harder braking and the problem goes away. Very strange.

 

Dave C

WEL653