When typing in the "Big Wheels" cheat(R1, X, Triangle, Right, R2, square, up, down, square)it doesnt accept it so load a saved game or start a new game and type the code again. Do this 5 or 6 times and the wheels shold be the size of monster trucks but only on the: cheetah, phoenix and infernus. but that doesnt mean that the code does not affect the other cars.after completing the proccess find a comet or a banshee and you should notice it is hard to control but if any car(apart from comet banshee and tank)hits your comet or banshee will go flying even a bus. Its great fun to get police away from you and the comet or banshee will become virtually indestructable but tanks blow them up.