Help with never ending brake judder

[jonbarrett]

Ever since I've owned the car I've had brake judder.

I've now tried two sets of front discs (one surface ground perfectly flat) and two sets of pads (Mintex and now EBC Red Stuff). Still the problem persists.

Here are the symptoms: from 70mph if I just touch the brakes lightly no problem. As I apply more pressure I can start the judder which starts to resonate through the steering wheel. If I then apply max brakeing I can stop the judder.

It brakes strong and straight. Just passed MOT. Bushes seem OK. No play in steering. Calipers cleaned and pistons free.

I have noticed one thing. If the car is reversing down an incline I get a slight knock when I apply the brakes suggesting something might be moving but everything seems tight.

The problem seems intermittent and worse if I'm braking in a straight line.

I'm running out of ideas.

[Peppe]

I had this problem, just after changing to EBC Red Stuff. If you read on the Swedish box for the pads it say that the pads will make noice for up to 600 miles. Mine didn´t make any noice but I had some judder for about 100 miles, after that everything has worked perfect.
The Red Stuff pads have a coating that should make the pads bed in with the discs, I think you can get both noice and judder before that the coating is complete gone.

I have just put on EBC Red Stuff in the back now and they made a terrible noice in the beginning but it has become a lot less in the last days now.

If you can´t get rid of the judder, get a micrometer that can measure the straightness of the discs. I did that on mine and the disks had a tolerance of about 10 thousands of a millimeter so that was not the problem.

[jonbarrett]

I let the Mintex pads bed in for 1,000 miles but it made no difference.

[kevin63]

First of all the clunk when you go from forward to reverse is the brake pads moving in the caliper, nothing out of the ordinary there, a bit of grease on the slides and a spot or two squerts of silicon sealant on the back of the pads will help or sort that problem out.
With the brake judder, I would suggest that you get the tracking checked (if you haven't done so already) my theory is that if not set correctly then when braking each wheel could want to go in different directions if too near center and with no toe in/out, this would cause the steering wheel to vibrate just like brake judder.
Good luck and keep us posted.

[jonbarrett]

I've had the geometry checked and wheels balanced. They noticed a slight buckle on one front wheen but said it balanced OK.

[GreenV8S]

I've seen problems like that caused by slightly worn top ball joints in the front suspension that led to very severe judder braking hard in a slight like. The usual cause those is 'warped discs' which usually means the discs have picked up the pad material unevenly. New or reground discs would correct this (at least temporarily), did your reground discs make any difference at all?

[jonbarrett]

Freshly surface ground disks made no difference. Would worn ball joints explain why the problem seems to be reduced if braking in a corner with the suspension and steering loaded.

[GreenV8S]

jonbarrett said:

Freshly surface ground disks made no difference. Would worn ball joints explain why the problem seems to be reduced if braking in a corner with the suspension and steering loaded.

Wouldn't say so with any confidence but it's not impossible, given that a side loading on the ball joint might help control movement in the fore/aft direction. It's pure speculation but well worth giving all the other joints in the front suspension and steering an extra good look over, since you seem to have eliminated the obvious causes within the brakes themselves.

[Peppe]

How does the surface on the hub look where the disk goes against it ?

If it has a lot of rust on it, it can get the disks to act as if they are warped. Try to measure if the disks are moving straitght on the car with the wheels of and bolted to the hub. Probably You need to put some shims in between the nuts and the disk to get the disks tight to the hub.

If they act a little warped try to move the disk one step at a time at different positions compared to the hub.

[jonbarrett]

No rust on hubs. I have noticed that I can get hub to move if I place a crowbar in the joint between the dragbar and chassis. However, this bush seems designed to extend out of the joint so I assumed it was designed to allow a little back and forth movement.

Would it be worth removing the wheels, bolting the discs tight and mounting a dial gauge on the chassis to see how true they run on the car.

[Peppe]

Sorry for my english but that was what I tried to suggest.

I did this and moved the disk in the boltpattern to find where I had the least side movement on the disk.
I used a dial with a magnet that i attached to the upper wishbone.

[saranigel]

I have this same problem with my car, the judder is not always there, but slowing for 70 or more causes vibration. Other times nothing- perfect!?
I am having this checked next month at PPC, if they fix it I will post the solution, it is the only problem I really have with the car so will be good if it gets done!

[jonbarrett]

Saranigel

Sounds like we have exactly the same problem. Very interested to find out how you get on.

[Tanguero]

Just a thought, have you checked/replaced your front suspension bushes. Free play in the lower wishbone can cause all sorts of odd symptoms.

[SI-PEN]

I had this problem early this year, I changed the disc and sorted the problem. Original discs were not warped and not badly worn but the vented disc fins in between the front and back disc faces were corroded and starting to collapse with heavy pressure.

[jonbarrett]

I think I'll be ordering some new bushes today just to try.

Re the discs, I replaced the old ones with a new set so they should be OK.

[jonbarrett]

Promised to report back.

GreenV8S, looks like you were spot on with the worn ball joint theory. You could not feel any play when rocking the wheel but with the suspension partly dismantled I could hear a slight knock from the upper ball joint. I've replaced the joint and the problem seems to have gone.

I'm replacing the other side tomorrow and then I'll give it a good test.

With the suspension apart it was interesting how tight the bushes felt.

[Storer]

I have the same problem but have not investigated it yet.

Ball joints are not that expensive so will be an easy starting point. I was thinking of replacing the bushes in the whole suspension and then having it set up properly as my car wanders at speed which I am told they shouldn't.

Thanks for the heads up. It may not be the cause of my problem but it is a good place to start after all the car is over 10 years old.