I’ve got a Lock-rite (Powertrax automatic positive-locking differential) in my Cruiser just wondered what happens if two different size tyres are fitted? Just before anybody shoots me down, different sizes I mean, same make and size. Lets say you get a flat and the spare has 30% tread on and the other 90% there would be a difference in the height (circumference) between the tyres, yes. What could/would happen to the drive train?