Urgent brake disc help

Post Thu Feb 16, 2012 9:33 am

Hi peeps. I'm having problems with brake judder on my e30. The steering wheel is shaking slightly when I brake and pulsing a bit.
I took both front wheels off and rotated the disc after bolting wheel nuts onto the studs. There appears to be tight spots if I rotate the disc. I measured the runout of the disc and it is out by approx 10 thou. I repeated this on the other side and got a very similar figure. I changed the brake disc for 2 new brembo ones (one at a time) on the same side and still getting the 10 thou reading on the dti.
The car has been fitted with a 3.8mm spacer between the disc and stub axle to push the 280 mm disc out to suit the 4 pots that have been fitted.
All I can think of is the hub is bent both sides (very unlikely) or wheel bearing issue. The wheel bearings don't feel really slack or noisy etc?
Any ideas?? Cheers

Post Thu Feb 16, 2012 9:41 am

What 4 pots? Are you fitting VW G60 discs? Are you checking run out with just the one disc retaining bolt in place, which is likely to give you false figures? have you checked the runout of the spacer before fitting the disc, any runout on the spacer will be magnified at the braking surface of the disc?

Ps) It's unusual to fit a spacer behind the disc, 3.8mm is not a stock sheet size so I guess they've had to be machined, which if done without great care is a very likely cause of your issues.

Pps) My 280 G60 discs + 4 pot wilwoods have a 2mm spacer between the disc and wheel to get the wheel offset back to stock, I quite quite work out why you've spaced the disc? It would be far better to move the caliper which would move it away from your wheels

Post Thu Feb 16, 2012 10:01 am

I'm using g60 discs yes, Mazda rx7 4 pots, I havnt tried running it without the spacer as it wouldn't fit. I did bore the centre of the disc last night to see if it was fouling on the mounting surface. Will try without spacer after work today. Measured it about 10 times with 4 bolts fitted (stud conversion).
I've owned the car for a out 3-4 weeks now so it's as was fitted when I bought it. I might remove the spacer and add a large washer behind the caliper to try it.
I've got a rally on Sunday so need it done asap. Thanks for your reply

Post Thu Feb 16, 2012 4:04 pm

On further inspection I removed the disc and gave it another clean up etc the refitted it and marked the hub and disc where the high spot is. I then turn the disc 90 degrees to the next hole etc etc until all four locations were done. All high spots on the disc was where the initial high spot I marked. So either the hub is bent?? Or the wheel bearing if that is possible?
The other side isn't quite as conclusive but still working on it.

Post Thu Feb 16, 2012 4:24 pm

Remove disc and spacer and use your clock to check the hub face itself.

Are you checking new discs here? Discs can warp if overheated and if warped would require replacement.

Post Thu Feb 16, 2012 4:28 pm

I've tried the original disc and two new un used ones as initially thought warped discs. Is used hard as a rally car. Do front wheel bearings make up part of the hub?

Post Thu Feb 16, 2012 4:35 pm

Yes the wheel bearing and hub face are a single replaceable unit.

You've got to check the hub face for runout, then the spacer for parrallelism.

It's not impossible that a hard landing after a jump could have bent the hub face on both sides, you can check this with your clock, I've never heard of it though.

See ebay for pictures of the assembly:

http://www.ebay.co.uk/sch/i.html?_nkw=e ... m270.l1313

Post Thu Feb 16, 2012 10:23 pm

I'll be buying some good quality hubs tomorrow so will keep you all updated. Thanks for replies

Post Tue Feb 21, 2012 10:47 am

Problem found. 2 bent front hubs/bearings. Dti now measures approx 2 thou with a rough trial. Hope brakes will now be good as Pembrey on weekend was a challenge with shakey brakey and locking up easily. Thanks for your help peeps!

Post Tue Feb 21, 2012 10:51 am

Post Tue Feb 21, 2012 12:36 pm

kipsy wrote:Problem found. 2 bent front hubs/bearings. Dti now measures approx 2 thou with a rough trial. Hope brakes will now be good as Pembrey on weekend was a challenge with shakey brakey and locking up easily. Thanks for your help peeps!

Well there's new one, must have seen abuse to bend them. Cheers for posting the update.

Post Tue Feb 21, 2012 3:09 pm

Thought it might help someone in the future! Havnt had chance to try the car on the road yet though so fingers crossed it works. Big rally on epynt in just under 3 weeks where will be lots of 120mph downhills on single track roads with no room for error. Check out you tube and type epynt rally