[Rachelsdad]

All good points, guys, and yes, we did discuss normal breakdown of the tire components over time. I wasn't seeing any issues on short runs, but the vibration was nasty, and really did feel like wheel balancing. What puzzled me was the "in and out* nature of the vibration, seemingly irrespective of speed (i.e., 65 MPH, vibration started...then calmed for a time, before starting up again - almost like a change in road surface). That was a warning sign which registered in the back of my head but never quite made it to my forebrain.

Indeed, the cost of a set of tires is miniscule in comparison to potential damage to the car, either from the steel belts flying about or from impact - and I am not even going to draw a comparison to potential injury or death.

Nope, no more moldy-oldies for me. My mistake was ordering those new tires before the car was ready to come home. They should have been part of the last phase of the work, in the weeks before the car came home from the shop.

Driving and enjoying the car: Absolutely!