Brake Vibration

Tropheus

Hi,

I replaced the standard pads and disks on my car almost a year ago (2003 Audi Allroad 2.5 TDi). The pads were EBC Red Stuff which came highly recommended. However, after about 5k miles, I started getting vibration through the steering wheel when braking. I was told it was the disks. I put back on the old disks (they were still in good shape) which fixed the problem. However, after another 5k miles or so, the same thing has started to happen.

It's obviously the pads that are causing them problem. I contacted EBC and one of their Techs sent me this. It doesn't make any sense to me. I did the work myself and they're suggesting the disks were fitted incorrectly.

Here's their reply:

This is disc thickness variation caused by having too much runout when fitted

Which is why it cured it when he had new discs fitted but it did not solve the problem because whoever fitted them did exactly the same both times and got the same problem

All discs must be fitted with a dial indicator and rotated hole by hole until the position with the least runout is found and fitted in that position

His only option now is to take the car to a procut centre and have them skimmed on the car

It is a fitting problem not a product problem

Slidey

I believe what they are saying is that when the disc is fitted to the hub it has a runout of is slightly out of line.

Personally I would be surprised if that was the case.

I was told when I enquired about EBC pads that it would be a good idea to only fit them along with grooved discs, how accurate this is, I don't know.

Are the Red stuff pads not for fast road/track use and the green stuff ones for road use?

Tropheus

I didn't think there was any adjustment to the caliper or disk to avoid the run out? I'm not sure how I could avoid this.

I had them originally with Zimmermann drilled disks which were also recommended to me. I was going to get EBC disks, but their expensive so went Zimmermann.

The Red Stuff are for fast road use, Yellow Stuff is for Fast Road/Track. EBC's own website recommended Red Stuff for my car which was probably based on the car's weight rather than performance.

I wonder if there is anywhere I can get the Zimmermann's skimmed? The disks look as though the pads are leaving an uneven deposit on them.

Slidey

ksimpson wrote: »

I didn't think there was any adjustment to the caliper or disk to avoid the run out? I'm not sure how I could avoid this.

I wouldn't have thought so either. I am sure the discs are made with zero run out. That only leaves the hub it bolts to which should be alright.

Have you checked the discs for run out?

There is a guy, think it is Mr.David and if I remember correctly he is a bit of a brake guru. Maybe you could PM him and ask him to comment

crosshair1

What they mean is that the hub will have some contribution to runout, the discs due to machining tolerances will also have runout.
I assume there is no locating stud on the disks and the disk can be fitted in any of 5 locations on the hub and they say its up to you to find the combination with the least runout.
I cant imagine this having much effect as initially when fitted you dont have a problem.
I have seen this happen a couple of times before and in each case it was due to seized slides/pad/guides.
Did you lubricate any of the components when fitting?

Mr.David

ksimpson wrote: »

Hi,
This is disc thickness variation caused by having too much runout when fitted

Which is why it cured it when he had new discs fitted but it did not solve the problem because whoever fitted them did exactly the same both times and got the same problem

All discs must be fitted with a dial indicator and rotated hole by hole until the position with the least runout is found and fitted in that position

His only option now is to take the car to a procut centre and have them skimmed on the car

It is a fitting problem not a product problem[/COLOR]

The reply you got is more or less correct. The problem will be runout - either in the disc itself or in the fitting of the disk to the car. Obviously a disc will always have a degree of runout (thickness variation) which is usually extremely small (a few microns) in a high quality brake disc. What then happens is as you apply the brakes, the pad heats the disc unevenly - the highspots becoming hotter than the lowspots. This makes the problem worse until eventually you get vibration due to the pad skipping over the high and low spots. If its a decent quality disc this should not happen.

The other possibility is that there is runout in the hub causing it. Or even a small piece of dirt/sand between the hub and disc would effectively cause runout. Hence its crucial to clean the mounting face before putting on the new discs.

The dial indicator will measure the runout in the disc and rotating the disc t different positions when mounting on the hub is good practise but usually not really necessary. The idea is to match the highspot on the disc with the lowspot on the hub to cancel out the overall runout. Obviously if you match the two highspots you will have considerable runout - this could have been the problem.

So in conclusion it was either the quality of the dics or the way in which they were fitted. Unless the pads are still very new I'd recommend changing them along with the discs.

Tropheus

Thanks guys. Sounds like I need new pads and disks. I find the Red Stuff pads very good bar the vibration, but will have to steer clear of then.