Juddering under braking

J

J-GTi-R

Guest
It only really happens if I'm braking from high speeds, i.e. coming off a motorway slip road, but when I brake the front of the car starts shaking and the steering wheel is all over the place.

I've change the pads for another set of Wilwood Poly-Qs, but that didn't solve it. I can't see any signs of warped disks, and I'd expect it to judder at any speed if that was the case, so I'm thinking worn suspension bushes or the like. I can't see any problems though, the drop-link bushes look ok, as to the ARB bushes.

Any suggestions?
 
G

gtir303

New Member
just a thought i had this problem and my discs seemed fine but when i took them to have them look at they said they were past skimming,throw them in the bin,my steering was fine it was only under motorway or harsh braking i felt the judder ,my mate can get them skimmed if it helps
 
G

GazTi-R

Guest
Had something similar years ago. Part of the internal structure of the vented disc had collapsed. There was no measurable disc run-out as the disc only warped when under pressure from the pads.

More likely as you say, suspension related. Weak/leaking damper could cause wheel bounce under braking.
 
J

J-GTi-R

Guest
Carl,

Yeah if your mate could give them a skim that would be great. I thought they might still be warped slightly, but didn't want to shell out £100 for new disks to find they aren't the problem.

Gaz,

I'll take the car around to a local garage I trust, get them to stick the car up on a hoist and see if they can spot anything.
 
J

jasegould

Guest
Why dont you get the run out measured :?: Thats the first thing you should do when your brakes judder, any garage should be able to do it
 
G

gtir303

New Member
J if u can wait till saturday the 8th may i can take it in to work and check all the suspension for u i will have to wait to find out about skimming the discs as my mates on holiday till next saturday let me know if any of this helps
 
J

J-GTi-R

Guest
8th of May is the Powerstation RR shootout and I'll be at that, otherwise I'd have definitely taken you up on the offer!

Jase, could you explain run-out to me? I've never heard the term but if it's a standard test I should find out about it and get it done (probably has a different name in NZ).
 
A

AJ4

Guest
theres two tests, on one a dial gauge is mounted next to the disc and the disc is rotated to see if it is warped. The other test the dial guage is put on at the centre of the disc and run out to the outside to see if the disc is wearing at an angle ( if you cut the disc in half the cross section would look like a wedge of cheese )
 
A

AZ STE

Guest
Make sure that the drive flange that the disc sits on is clean and the disc matching face is clean.Any slight imperfection here will throw the disc out when you tighten the wheel up and cause juddering at hig speed.
 
GTIR-LOZ

GTIR-LOZ

New Member
could also be pad judder which can be caused by air in the pistons, i have exactly the same problem and everytime i bleed them they are ok for a while then it comes straight back - very anoying, please let me know what you come up with
 
A

AZ STE

Guest
J
when I first got mine I blead the whole system with Castrol dot 5 (silver bottle) from halfords 1 litre. The old stuff that came out was really nasty,keep bleeding each caliper until it is nice and clean :wink:
 
J

J-GTi-R

Guest
I had AP Racing dot 5.1 put in when the kit went on, it was a complete system flush too.

I just got the car back from the garage (missus is away, so I couldn't bleed the brakes myself). They took the wheels off and spotted the problem immediately. The disks are absolutely fecked, the surface is covered in tiny little cracks and they reckoned I shouldn't really drive the car as it is. I didn't spot the cracks as I checked in bad light!

Conclusion is the solid disks I have are not up to the job, they really need to be vented or cross-drilled, as the disks are getting too hot and cracking. I've just rung up Rally Designs and ordered some vented and cross-drilled disks, which weren't available when I bought the kit.

I'll report back if this does cure my juddering.
 
C

Curtis

Member
What did Rally Designs say when you told them?
Are they taking them back as you've not had them five minutes? :shock:
 
J

J-GTi-R

Guest
The brake guy wasn't there when I rang so just ordered the disks anyway, as they need replacing ASAP. I've had them a year and have been using them very hard (I love late-braking), so I'm not expecting a warranty claim or anything, but I'll send them the old disks so they can have a look.
 
K

kyepan

New Member
J's discs had a harsh upbringing, used and abused, then abandoned when they were coming of age.. good luck with the new discs..
 
J

J-GTi-R

Guest
Damn right they had a harsh upbringing, a week after I had then put on I was lapping Castle Coombe...

Yeah cheers Carl, I should have checked properly, but they should be sorted soon!
 
You must log in or register to reply here.
Top