@roottoot

sounds like you are talking about different "regular" sized tires with different pressure,

i'm about case when installed OEM spare wheel which has -5.3% in diameter / circumference

 

 

Anyone daft enough to have as a spare such an undersized wheel / tyre and then put it on and drive with it really needs to give themselves a shake.

The head cases that run about for weeks with skinny space savers on for weeks even at uk motorway speeds are ignored even by police officers.