[Grover432]

I'm confused by this statement:

‘With the new car we have been able to choose a new tyre size, keeping inflation pressures on the healthy side. If you have a smaller wheel, you have a smaller air volume, therefore need higher pressures.’

If the wheel is smaller, but the overall OD of the tire is the same as with a larger wheel and shorter sidewall, wouldn't the air volume of the smaller wheeled assembly be greater (assuming the same width tire) allowing for a lower tire pressure on the smaller wheel tire combination??

The bigger wheel would have a shorter sidewall with the same OD - extra space being taken up by the greater diameter wheel would that be the case??