My A3 was new in Oct 2015 and has covered just 4.600 miles. (and driven very carefully)

A week or so ago I noticed that the O/S/R brake disc was rusty and scored, the remaining 3 were smooth and polished as you would expect on a car being used daily.

My Audi garage put the car on their Dyno test rig and found no brake fault.

Having been in the trade for over 40 years I argued that this is not normal as they suggested...............(1 rusty disc and 3 polished ones) but they insisted that there was nothing they could do or replace under warranty.

I am astonished that they released the nearly new vehicle with no detailed investigation into the reasons for the rust, their only comment was "that this was a NORMAL" thing to expect.

Hi Ron...welcome to the Forum!

That does seem quite odd. Sounds like the rear brake isn't working so well on that corner (sticking pad or slider)

Would be tempted to spray or paint something (engineers blue for example) on it and see where exactly is the contact area.

Let us know how you get on 

Regards,   Trevor - Admin