[enigma]

I've seen a few causes.

1: Sometimes wheel weights get knocked off or lost when pulling wheels on/off the car.

2: If the wheels were out of balance the spacers would magnify the effect.

3: Its possible that the wheels didn't seat correctly on the hubs. Did you lower the car to the ground before torquing the wheels? I have had better luck torquing the lugs before putting substantial weight on the wheel (i.e. lowering the car more than was necessary to keep the wheel from turning).