I have 3 Y.O. Continental Conti Comforts on the rear of the 2010 C5. After 48,000kms there is still plenty of tread left. Over the last 12 -18 months however a very annoying sort of "wirring" sound has developed and emanates from the rear of the car. I took it to my local Tyrepower centre, and they removed and inspected the tyres and showed me that the tread blocks on either the inside of the tyre or the outside (can't remember which) were castellated. Tyrepower suggested that "my shock absorbers were worn out/ faulty", but as the C5 doesn't have any in the normal sense, and rides and handles perfectly, I said I doubted that that was the case.
Is this normal? I know the rear tyres have lasted a considerable mileage (the front ones were replaced with Michelin Pilot Primacy about 12 months ago after 35,000kms), and I never had them moved periodically front to rear because I never wanted to face the prospect of buying all 4 new tyres at $280 each at the same time.
So my question is: Is castellation/scalloping on the rear tyres of C5's after a large mileage normal, or do I have a suspension problem?