I am a very big fan of GSD3's and have been running them on my A4 for around 17,000 miles. I had to change one of the back ones and up due to damage. On monday of this week I noticed that the smooth part of the tyre between the rim protector and the actual alloy was splitting in several places, some as long as 50mm. The two fronts (one is the splitting one) still have 5mm on them. I have spoken to Goodyear who want to see the tyre to pass comment. Surely this is a fault as there is no damage to the tyre or alloy. I am now running the new tyre on the back. My next question relates to the tread left. I have 5mm on each front as I moved one from the back to the front to match the remaining front one. The new one went on the back to pair up with the other newish one which has just over 7mm on it. Is this all o.k as a set-up and on a quattro?