[sanddrag]

There is no "best wheels" There are a lot of other factors. What you are experiencing is too long of a wheelbase, too narrow of a track width, too much traction, or any combination of the above. Many teams use 6 wheels, with the center ones lower, so only 2 or 4 can be on the ground at a time. Some teams use omni wheels on one end. Some teams use high traction wheels and low traction wheels. Watch some robots, see if you like how they drive, then find out why they drive so nicely. There is no clean and simple best.