What if the old tires are 8 and you just want to replace 1 new that's usually 10? Seems silly because the only damage they can do is with a differential, lsd or xfer case and that would have to be 4/32 or more difference with extended use.

In the US, if you have a puncture on the edge you're not allowed to repair it and the legal limit is 2. 4/32 is the recommended tire size difference for awd or on the drive axles to change tires and they have to be the same brand, but not legally required.

2/32 is rediculous for the legal limit though, should be 4.