Originally Posted by froudeg
Just to add to this - i notice you say it feels like its coming from all over the chassis, and in the steering wheel and the seat.
It's hard to tell if its actually coming from the steering wheel when you feel it all over the chassis.....usually a vibration from all over the chassis, especially one thats felt through the seat is a problem with the rear of the car.
This could be rear wheel bearings, rear suspension bushes, damaged control arms or a severe alignment issue (camber or toe badly out).
Problems with the front wheels/suspension/alignment usually are felt far more in the steering wheel than anywhere else - if it feels like the whole car is shaking/vibrating (especially when coasting in neutral, pretty much ruling out engine mounts etc) i would concentrate on looking at the rear.
I think you're right about it being something in the rear, there really isn't much forced rotation in the steering wheel, just the chassis vibration that is felt all over the car. I'm measuring the rims, tires and brake calipers with a dial indication this afternoon, that should show what is out of round.
Originally Posted by xeno555
Yes it is pricey. Also when you remove the wheel (one that has been road force balancing (RFB)) without marking the position on the hub/rotor, you run the risk of making worse. This is because RFB balances all rotating mass per wheel.
You could view your car (wheels) from another car while someone drives yours @ 65 MPH and see if any of the wheels looks bent or wobbly.
Another thought, you said you tried many rims/tire combos. Did you ensure that the correct rotation of the tires are followed correctly. Correct tire pressure also.
Xeno555, Thanks, I'd only had the rims/tires road forced balanced and haven't tried the on-car balance. After I make sure the rims/tires/brake discs are true today, I'll try to figure out if that balance is necessary. The vibration I have is so great, it's got to be more than a balance issue (unless they REALLY f'ed up the balance). That's a good idea to have someone else spot the tires.
I did check tire pressure on all of the other tires I've tried.