Replacing rear discs on an S3

Yes, for sure needs to be replaced. It’s called a “dust seal”, not a rain seal. :grimacing:

I agree with Jerry, definitely needs replacing. Besides rain, you also need to worry about dust, humidity, and just plain air.

I am concerned about just what could cause such rapid deterioration, though. Did you apply any lubricants or other products?

I have heard it suggested that, when assembling gaitors such as these, they should be coated inside and out with red grease, the stuff intended for lubricating Girling rubber stuff.

To me it doesn’t look that the rubber has deteriorated by itself, but rather that somehow it got in between the piston and the brake pad and squashed to death. You can see the compression marks.

There is no deterioration oin the rubber that I can see.

It looks to have been pinched. Using red grease in assembly would allow it to slide and move a bit so it would have been easier to slide into the groove equally all of the way around. Ditto for the piston.

It’s the same when assembling a bicycle tyre into the rim. You go around the rim pulling and pushing after it is in so that the inner tube is not pinched between the tyre and the rim.

EDIT :- I don’t see any evidence of copper grease on the back of the pads. Perhaps they welded themselves to the dust seals, pulled them apart and they got crushed when pushed back in?

kind regards

@Aristides, @Kirbert, @Jerry_Mills,
You have all confirmed my own thoughts. Replace !
Also, to me it sure doesn’t look like deteriorating but pinching. I did use copper grease and as far as IIRC also red grease when assembling everything, but that is a little uncertain.
New dust, not rain, seals are on order and the car will be off the wheels for an other week.

Thanks for your help y’all …