I know G27 and it does adjust automatically depending on the car your driving in GT5.I use a g27 and it came with the logitech software which i used to lower the rotation degrees on the wheel.
I am not sure if it actually made a difference in the GT5 game but I think it did , this isnt proven though so im sorry i cant provide any facts.
You should give it a try thought if you use a g27.
Im not buying a G27 because its old now and its looks crap.