vibration
 

Just before leaving for parade I had new tires and a balance don on the 04 boxsterS. Noticed a vibration between 45 and 70 on the trip that is pretty noticeable, in fact it vibrates the driver's side mirror bad enough to make it distort the image of cars behind. My first thought was drivers side front tire as the mirror on the passengers side did not seem to be affected. However, I am starting to wonder if a front motor mount might do that. It has the original mount in it and it is time for a new one. My balancer is usually very good. Anyone able to shed light on a similar vibration?

My experience is failed mount creates a "clunk" when shifting/accelerating but not a vibration. Why not swap your tires and see if the problem follows the tire to the other side?

Take it back to the shop that sold the tires to you. If the problem didn't exist before, its more than likely something they did, bad balancing, new tire thats out of round.

Don't know if it's still true but I was taught speed sensitive vibration is almost always a balancing issue.

Back to the tire shop and it was a badly bent REAR wheel. Sure was obvious thru the steering wheel. Still not sure how it got bent. Going to change the motor mount soon as it is time anyway.