Not to beat a dead horse.. But....
Modern car tires can change shape, but not size.
I actually measured.
The tire acts like a leather belt, not like a rubber balloon. It can come close to a circle with lots of pressure ( or no load ) or it can be like a tank tread, with low pressure and lots of load.
A Ford Escape Tire with 48psi and loaded = 2100mm perimeter. ( not a circle )
A Ford Escape Tire with 48psi off the ground = 2100mm circumference.
A Ford Escape Tire with 35psi and loaded = 2100mm perimeter.
A Ford Escape Tire with 35psi off the ground = 2100mm circumference.
A Ford Escape Tire with 20psi and loaded = 2100mm perimeter.
A Ford Escape Tire with 20psi off the ground = 2100mm circumference.
This came up on another group, and there were lots of theories, so I measurerd.
You can't say this is due to the "steel belt" because "radial" tires mean the belt goes accross the tire ( sidewall to sidewall ) NOT around the tire. Bias tires have the belt going around the tire circumference. Bias tires do not hold up as well.
Radial tires can spin either direction, so you can rotate left & right. ( or X )
Bias tires always have to spin the same way, so you can only rotate front to back.
- John