the new tyres are 2.13% smaller diameter than standard or 13mm.
When your speedo reads 60mph you are actually doing 58.7mph.
The tyres are safe on the rim - they are not going to fall off or anything, MINI were just pointing out that you were running a non standard size and your speedo is slightly out.
Most authorities suggest keeping the size differential to less than 2.5% so you are fine
John |