[kamesama980]

I would imagine it depends on the GPS manufacturer as to whether it accounts for the Z axis as well as X and Y. and what it was intended for. Cheap ones probably do not. expensive ones might. ones meant for off-road use as well most likely.

I go by GPS over odometer. Odometer only has to read within X% from the factory. That's going to be averaged across a few similar but not identical tire sizes at a certain pressure, and in my case I run larger tires at higher pressures in all my cars. I correct the Cressida +15% with the winter tires on: 215/65R16 vs 195/65R15. Take that winter mileage :-D