Rear tyre wear

My 2001 Audi RS4 B5 with 235,000 miles has worn inside edges on both rear tyres. The wear pattern is cupped – there are noticeable peaks and troughs in the wear around the circumference on the inside edge. The problem was identified recently when I took the car for wheel balancing due to vibration.

Eighteen months ago, the front tyres were replaced at 212,000 miles. The rear tyres were replaced last year at 216,000 miles and a four-wheel alignment check and adjustment was made at the same time. The rear springs and suspension brackets were replaced at 190,000 miles, three years ago. At the time there was a question about which of two spring options was correct – if the wrong springs were fitted would this cause the tyre wear?

I was told at the last service, three months ago at 229,000 miles, that the self-levelling suspension is not working, but this was not repaired. I’m not familiar with this system, but could it be a factor in the tyre wear? At that time, no mention was made of excessive tyre wear on the inside edges by either the garage, a local VAG specialist or the completely independent MOT tester. The tyres are currently legal, but the vibration is increasing steadily.

During the past year or so, various front suspension components have been replaced but there has been no work to the rear. As far as I know, the front and rear dampers have never been changed. As the suspension travel is short and the springs very firm, a bounce-check for damper effectiveness is inconclusive, and there are no obvious leaks. The car passed its MOT in January, with no rear suspension issues advised. Is there any other way to diagnose the damper performance in situ and confirm this as the problem?

Without any other way of confirming the diagnosis, I intend to replace the rear dampers and then have a full four-wheel laser-tracking check and adjustment. Do you have any other suggestions? Is there anything else you would recommend I check and/or change as a matter of course when the dampers are replaced? Pat Brooks If the wrong springs were fitted, this would affect the ride height of the vehicle and the rear wheel camber. It would also result in wear on the tyre edge, but this would more likely be a smooth wear, not the cupped wear that your tyres are exhibiting. This would also have been picked up when the fourwheel tracking was last carried out.

The self-levelling suspension is called Dynamic Ride Control (DRC) by Audi. The system pressure should be tested at 22 Bar. This system will need to be checked before replacing the rear dampers. It does require specialist equipment (part number VAS6544) to empty and refill the system. Once the new dampers are fitted, the system should again be checked for leaks at 22 Bar, then the pressure should be dropped to 16 Bar.

I would certainly suspect that the rear damper problem is causing the tyre wear, but this is coupled with the inactive DRC. For this reason, I would advise that the DRC is rectified before going any further.