48 replies to this topic

[Andrew aka Stuwy]

So a few times I have been on track with the new VX and I think I know now that my issue is not brakes (happy to be told otherwise). The story starts in midsommer (national last year) in the afternoon sessions I had a very slight vibration only under heavy braking. As I was on borrowed wheels I dismissed it as nothing and not had anything since. Till Brands hatch! Again in the afternoon once the car was at track temps and during braking I then got more steering wheel wobble. I assumed I had warped the disks as they were really cheap. Replaced the disks! Thinking I had solved the issue I was on track last weekend at rockingham. Again once everything was very hot, the shaking has developed to shuddering it was ok ish in the morning and got progressively worse through out the day. Me and Mbez was thinking that it could be the hubs/wheel bearings? I can't get it to do this on the road. Abs was off. Wheels and brake disks have been different. Pads are 1144s and was put in before the National last year, can these cause it? A thin film of something has appeared between the wheel and disk, front only... Any suggestions ideas or advice?

[fezzasus]

I'd be looking at the bushes. If you can't get it on the road it might be because the suspension isn't under the same compression while braking.

 

Just a guess though

Edited by fezzasus, 21 April 2014 - 06:58 PM.

[anz3001]

Pads could be leaving deposits on the disk with the extreme heat track braking brings? again just a guess. 

[drunknmunky]

If you severely overheat pads, they can glaze on the surface, and this can lead to a blue appearance on the discs aswell, as anz says, they can leave deposits on discs when hot. I'd try higher rated pads for one. You can try taking the ones you've got in out, lightly sanding the surface to get rid the glazing, then put them back in though be very careful, as they would need properly bedding back in if you try that. Is also a guess but I've done similar before, though admittedly not a vx, a much bigger heavier car.

Edited by drunknmunky, 21 April 2014 - 09:26 PM.

[Claws]

Mine did this on my last track outing after they got hot, got to the stage where I didn't have much confidence in them once warmed up. 1155s, nearly 2 years old, about 15k on them, disks the same, fluid a lot newer. I have put it down to a combination of old pads and worn/warped disks. I will be replacing the pads, disks and fluid soon, as well as giving the calipers a refurb and new fluid. I can replicate it on the road if I really stand on the brakes on certain roads. It's mainly the NS front. Perfect when cold and not worked really hard

Edited by Claws, 21 April 2014 - 09:49 PM.

[hairy]

Are they different pads front and rear? May be they are providing different friction rates if fronts are glazed?

[Andrew aka Stuwy]

Same pads front and rear. They were bedded in properly. The shuddering will only happen after about 3 or 5 laps. The whole car shakes. Braking performance is not changed I still have full braking and good braking at that too.

[fezzasus]

A thin film of something has appeared between the wheel and disk, front only...  

 

I would inspect the seals on the calipers.

[JG]

Warped disc is a bit of a misnoma. Usually it is because of the transfer layer on the disc being inconsistent I don't actually know how you fix it without replacing the discs, but a very hard track session can work it through.

 

 

[Mr Apex]

I had the same issue, albeit mildly, on the last track day I did. It happened consistently once the brakes were hot at the end of the straight at Castle Combe. My main concern was that it happened in the wet, when braking forces are obviously reduced, so it could get a whole lot worse in the dry. Pads are 1144s front and standard rear. Bushes are all good, discs are good, front calipers have recently been rebuilt.

 

No idea what the cause was, but there is a common theme in this thread with pad make...

[slindborg]

I'd go with it being the pads... they are the 'only' thing you havent changed to keep the same symptoms (and the bushes)

 

1144's are excellent road pads but for track they are just cheese. 1155's, PFB 97's, CL whatevers, pagid RS12343257465389564 etc are all better tools for the job.

[CocoPops]

Sounds familiar. I had a similar issue at snetterton recently. Hotter they got the more pronounced it was. I'm running ally bells and discs, with pagid rs14

[Steve.i.am]

http://www.vx220.org...e-kit-problems/

 

I know its a different setup, but symptoms seem the same. Inconsistent xfer of pad layer to disc.

[Andrew aka Stuwy]

Thanks all for the suggestions. I'm going to pull it appart tonight (weather permitting) and take some pics to have a look. See if I can find anything obvious

[Nev]

Bushes or bearing packs IMO. Good luck, not an easy thing to localise without lots of possibly expensive swap outs.

[Vaux Pop]

I had vibration through the steering wheel under hard braking at Goodwood last month. CL6 pads in AP 4-pots on Pagid 2-part discs. 

 

Discs turned out to be 10 thou out of true. Since being skimmed, brakes are good, but I haven't been on track since so don't know for sure if the problem is cured.   

 

[Andrew aka Stuwy]

Right. Wheel off. Played with everything I can and I can't find any play. No splits in the rubber bits. Pads seem off colour? Disks go part of the way round with little effort and then need more effort to get past a certain point. The mistory grease is nothing more the copper ease.

[TheHood]

Do you have any way of measuring the disc runout accurately? Ideally you'll need to have or bowwow a dial gauge and stand. TIS says maximum permissible runout is 0.03mm

[Claws]

I checked mine earlier, just a worn disk on the inside, as I suspected.

[Andrew aka Stuwy]