When I was at the Ring a couple of weeks ago, I coasted for the last couple of miles to the end of my last lap because the car suddenly developed an extreme judder that felt like a collapsed bush. The judder was enough for me to fear for the health of the steering column.

However the car continued to steer straight ahead, and as soon as it cooled down it was fine again. On the way home the following day I was pushing really hard on the road to Monschau and it started to happen again.

I'd lifted the car the previous evening to look for bush failures or loose components, but didn't find anything. The brake discs are 3 months old ATE, and the pads are Yellowstuff. There was no binding when I lifted the car, but the disc surface looked slightly different to usual, but no blue discoloration.

Can judder that is only present when the car has been driven hard for some time, be anything other than brake related?

I had intended to give the car a shakedown at another trackday this weekend, but the fuel leak has scuppered that idea. I'm still not entirely sure whether it happens in straight lines as well as when I brake hard immediately before turn in.

Alex (Cheburator) has suggested that this is very likely due to pad deposits from the EBC pads and my gentle/progressive braking style.

http://www.ebcbrakes.com/troubleshooting.shtml

EBC reckon it's my fault for not checking the run-out when fitting the new discs, which is true I didn't. However I did spend a long time cleaning the mating surfaces on the hubs.

Any thoughts gratefully appreciated.

 

I've been battling hot brake judder on my car for some time now. I found loose wheel bearings on pass side and correcting that made a good improvement, but still having the problem. The obvious suspect is warped rotors, but I always thought you'd notice pulsation with a warped rotor whether hot or cold. I may eventually replace all the rotors but would be interested in knowing other things to check for ... for example, someone posted once about worn out flex lines that don't fully release the pads and perhaps cause heat buildup.

 

My front judder turned out to be out of round issues with both front tires (tyres ). On the balancing machine you could see the out of round also had a lateral movement of 1/4-1/2 inch. New tires made my problem go away completely. YMMV

 

I hesitate to tell this, but for what little it might be worth, I'll go ahead.

I had a similar situation with my wife's Cad, particularly and only when going down the other side of some/any of the mountains around here. When the brakes got hot they pulsated pretty heavily, but only then, not when they are relatively cool around town or on the flat roads.

So, I ordered some nice cross drilled and sloted rotors off ebay and changed them out. One thing I found was that one of the front rotors I had taken off, although not worn much, was poorly cast so that one side of the rotor on one "end" was much thicker than the other side. I thought I had solved the problem and, except for the new growl that the brakes seem to have with the new "sport" rotors it ran smoothly.

That is, until the next trip down the other side of the mountain, where I found that not as much but most of the hot brake pulsation was still there.

The part about this that I hesitate to pass on is that I related this to a couple of gear heads I was talking to somewhere and they both related that in order to cure this you need to flush out the old brake fluid from the system. That sounds so non-intuitive that I haven't done it--yet. I am going to do it when I can get around under the car, but I really have my doubts about why that could possible make any difference.

If you fall for this idea and actually try it before I get to I will be real interested in the result. At least it can't hurt.

Jerry Feather

 

its possible you have warped the rotors,
Make sure you fresh brake fluid in the system
i would also check the wheel bearings for proper adjustment,
and the inner and outer tie rods the inners are a lot harder to check,
BUT with assistance have a helper turn the wheel back and forth about an inch( engine running) while you lay on the ground and look at the rods as they move it might be easier if the boots are removed from the rack body to see if there is play,
Otherwise if the tie rods are original it would be a good idea to just replace both sides

 

Additional info:

Brake fluid - flushed with ATE Racing Blue when discs/pads were changed
Wheel bearings: overtight, yes I know they will fail, but I don't care (I carry spare cages)
Tie Rods/ends: replaced within the last 20k
Run out - still not checked

The car is pretty much only used for track days at the moment (even though it is almost entirely original), so my main focus is brakes.

 

you could have damaged the hubs with overtightened bearings,

Remember that the hubs grow when they get hot, and if you have them overtightened ( the bearings) then you may have fried your bearings,
it would be better to have them a bit loose than tight.

if the spindles have worn on the lower inner bearing seating surface then the wheel will never be totally free from play,
this is OK as long as the bearing washer can be pushed with the tip of a screwdriver

 

Aside from needing a fresh rotor friction surface, and you probably do have uneven deposit issues, you might need inner tie rods.

Here's what happens:
You put some sticky tires on your car and go to the track where the car sees more braking force than it ever has. The steering linkage is forced inward under hard braking and now it's being forced in really hard and this collapses the 20-30 year old plastic liner of the inner tie rod. This then amplifies braking vibration and you feel like the car is coming apart.
That happened to me on the first track test when I built my racer.
Jack up your car and see if you have play on one side. Even if it's not a problem now it will be something to consider as an easy to foget about part that should be replaced on a track car.

 

Mike, he said the tie rods were replaced 20K ago but i would concur with them being bad,
there is an inner and outer joint on each side of the car both sets should be replaced

 

Maybe it's all in the pads/rotors but I'd be surprised since he mentioned the steering column.

UKKid', do you know about bedding? Most race pads require a pre-use process of heavy repeated stops to heat the pads up and transfer material to the rotors. On race pads this is very important. Your brake supplier should have specific bedding instructions if that's required.

 

It should go without saying that anything mechanical can fail at any time, so don't assume that just because some component is relatively new - it's not the cause of the problem.

Check everything!

James

 

It sounds like deposits on the rotors from not using a proper track pad. The deposits can be scrubbed off.