Whenever I need to get new tires, I just bring them in "loose" so they don't have to install them on the car. Just mount the tires and balance them and I'm good. I'll put them on the car myself.

Though the guys at Discount Tire insist that I can bring them in while they're on the car and they'll do the work for me, I just have better peace of mind if I install the wheels onto the vehicle myself.