Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Wavy Brake Discs on 4/4

I once bought a pair of discs for my MGB, When I fitted them, one was perfectly concentric on the disc part, but the centre section was visibly eccentric. Amazingly it didn't cause imbalance so I left it.

Hallo Heinz,
I'm on my 5th set of disc brakes in 60000kms (Morgan 4/4 Sport 2009) and once again the brake judder is already appearing.
Sadly I recognize all the symptoms exactly as you described them in your topic.
The first 2 sets were replaced under warranty; the last 2 sets I had to pay for, also for new brake pads.
I drove 80000 kms in my previous Morgan (4/4 4 seater 1991) with the same set of brake discs and pads and performing the same driving style (quite leisurely).
The dealer in Belgium has no explanation for this recurrent brake problem.
Please let me know if there is a solution to this problem.
D'Herde Bart

Hello D'Herde Bart,
when I have some news, or better than that a proper solution, I will share it here and I will PM you also. Do you say that with your previous 1991 4/4 4 seater you managed to drive all 80.000km with the same one set of discs?

Heinz,

My 4/4 has done 99,000km and still has original discs.

Probably a separate issue but as discussed on another thread, the front pads have a tendency to stick if the car is put away wet. Interestingly this causes the brakes to juddder which is felt via the peddle. The marks on the discs from the stuck pads are still noticeable several thousand miles later. In my case it was around 500 miles & lots of hard braking before the judder stopped.
I wonder if this phenomenon causes an incorrect diagnoses of the disc being warped when in fact it is the disc friction surface. Mine so far have done 25000 miles but I do have an issue with the offside inboard pad not covering the complete disc surface. The brake unit is scheduled to be stripped down next service (April)

I have read morer information (in German) now and it seems that the amount of cases where judder is caused by areas of different friction is huge. I will have a look if I see marks on the discs caused by the brake pad, as this was the case after the examination of the second change of discs. I now have learned among other infos that it is very important to run in new brakes and pads to put an even film of the pad material on the disc's surface:
Brake down from 60 mp/h to 6 mp/h in a bundle of sequences, never stop rolling, allow to let the brakes to chill within the trials and brake with rising force from one attempt to the next one.
Unfortunatelly I did not do so and this is new knowledge to me.

Also it was warned to stay on the brake pedal when idling after having done a sporty drive with hot brakes.

A different issue that if someone changes the discs on an hub, it will cause strong judder if the hub was not smoothed totally even, any rust has to be taken away even if it is only 1/100 of a 1 mm prominent.

Heinz,

it does seem that the problem is, as you suspect, uneven friction due to the disc and pad not working well together.

Some web research led me to THIS article: it seems logical and covers a number of other brake related issues.

So, I think the answer is simply to have the discs media blasted, not skimmed, and then to bed in new pads on to the clean discs.

As an aside, after washing the car I try, whenever possible, to dry the pads/discs by going for a drive and doing 4 or 5 firm stops from 60-80kph, just to the point the ABS cuts in, about 0.8g. The Plus 8 discs rust very quickly, like the discs on the AMG and my bikes. From memory the discs on the roadster didn't seem to rust as easily/quickly.

Good luck with this.

Thanks for the article, Peter. Funnily enough I found the same article in a German translation.

Perhaps a set of carbon-ceramic disks will cure the problem permanently. They also save weight both on the car and in your pockets.

Harald

a friend have a Cayenne 12 years old, the ceramic brake disk cost more than the car value