[MaSnaka]

There are a few tire shops which can do it while the tire is on the car. Old school machine spins the tire while one end of the car is jacked in the air and the tech puts his hand on the body to feel vibration while guessing and checking with weights. It's an art. Cost is around $30.00/tire but when I had it done the guy wouldn't do the rears. Not really sure why not.

You still need a way to get your tires loose though and I can't speak from experience but the spinners turn to the rear of the car. Passenger side counterclockwise, drivers side clockwise. Somebody correct me if I'm wrong. Then to install use some antiseize on them so they don't get stuck again.

John