Originally Posted by Nikolas
I don't know of any AWD car that doesn't do this. Which one's are you referring to? Porsche as an example matches rotating diameter - at least mine does.
Which Porsche do you have? Porsche has a couple of different AWD systems. I can tell you that, unless you have a 997 Turbo (2006 or later), or a 2009 Carrera 4, you likely have a viscous center coupling, which is quite sensitive to small differences in circumfrence. xDrive does not use a viscous center coupling.
The Cayenne doesn't have a viscous coupling, but it does have low-range gearing, which presents its own set of problems for mismatched tires.
May 3, '07European Delivery, Redelivered on 6/11/07 - Monaco Blue/Beige, Steptronic, ZPP, ZCW, PDC, iDrive/Navi with RTTI, Logic 7, Xenons, HD Radio