My 9-5 (year 2000, 78,000 miles/125,000km) has been giving some vibration for a while. I had the rear tyres balanced, discovered that there was a ding in the ALU22 rear rim, so I took that to be replaced and have the rear balanced again. Problem remained and started to be apparent through the steering wheel as well as through the seat. Took the car to have the front tyres balanced, they were apparently well out (how, I don't know, but they were), so they were balanced up. I asked the ATS tyre tech to check the rear ones again, when he took the first tyre off, I thought it was odd that he called his hoppo over to have a look at the tyre, then again with the other rear tyre. He called me out of the waiting room and showed me the two fairly new tyres (Avon) They had about 10 or 12 flat spots and peaks around the inner 1/3rd of the tread on each side. Apparently it was as though the car had been bouncing along the road rather than rolling along it. Bouncing the rear end of the car doesn't seem to suggest that the shock absorbers have gone, neither does it feel like the car is wallowing when driven.
What could be the cause please?
I have owned the car from new, it hasn't all been happy, but despite that, I still like the car.
Pete.
I know I wrote octagonal, then increased the number of flat spots to 10 or
12... what is a twelve sided shape? A dodecahedron or something, and a ten sided a decahedron?