When I got my bus it had normal car tyres on 15" Empi copies with about 32psi in and when I first drove it in a crosswind I thought I was going to start bouncing off other cars. It was very scary. First fix was to put max pressure in all tyres, this made a big difference but still not great. I then got some stock steel wheels with C14 van tyres on, fronts wouldn't fit because of the narrow beam, so I put heavy duty 4x4 tyres on, now it drives well and is hardly affected by crosswind. The rear van tyres are at about 50psi and the fronts 40+. It's all to do with the load rating. Having said that my bus isn't that heavy 1200kg ish.