3Scanner

from a Passat W8 and was thinking of installing them on my S4...

I checked with the dealership for fitment issues and was told that these would work on the S4.

One of the rotors has significant scarring on its surface. My questions for the pros:

1) What could have caused this problem?
2) Is this rotor still good or is it pretty much hosed which means I shouldn't install it on my car?

Please take a look and advise. TIA for your help.

<img src="http://pictureposter.audiworld.com/43051/w8_front_rotors.jpg">

Closeup view
<img src="http://pictureposter.audiworld.com/43051/closeup_of_scarred_area.jpg">

Profile view
<img src="http://pictureposter.audiworld.com/43051/profile_of_scarred_area.jpg">

ModifiedA4

wierd that looks welded..

Mike2kS4

A picture aimed at the vent side should give a better idea on what we're looking at here.

3Scanner

Thanks for the info, Mike. Can you clarify what you mean by turning the rotors? Is this simply flipping if around to make use of the brake surface? Below are photos I just tood of the opposite or vent side of the rotor for you to check out. The tip of the plier indicates the location of the scarring on the other side. Thanks for your help.

<img src="http://pictureposter.audiworld.com/43051/same_location_vent_side.jpg">
<img src="http://pictureposter.audiworld.com/43051/closeup_of_vent_side_jpg.jpg">

Mike2kS4

How about a picture looking towards the rotors vent surface where the defect is, so a gauge of its depth can be made.

3Scanner

The end of the ruler points to the scarred location on the rotor surface as a point of reference.

<img src="http://pictureposter.audiworld.com/43051/rotor_vent_location.jpg">

SilverA4Fun

it looks like a ball-peen hammer was used on it

Mike2kS4

Whatever it was, seems to have penetrated deep (halfway) in the metal. That rotor is no longer sound.

3Scanner

Thanks for your help, Mike. I really appreciate it. Will do!

WindyCityS4

It is not serious. Here is my guess..
Some sort of chemical (acid would be my first guess) got onto the rotors. The splatter pattern suggests a liquid poured from significant distance (&gt;4"). Since the rotors are used, there is a layer of pad material on them. The chemical reacted with the metal under the pad mateial and released a gas, my guess hydrogen from the acid. The released gas caused the pad material to blister. If you are lucky, the pad material could be srcaped off to reveal a fairly undamaged rotor surface. If you want to save them, I would suggest having them turned as Mike said. I wonder if the seller tried to use some chemicals to "shine up" the rotors and remove the rust. Too bad there is no issue with the rust.



But you need to ask if it is really worth it. Catastrophic brake is not a pretty picture.