Torsen work by sensing torque difference instead of speed difference like viscous. Old Subarus got viscous center and rear diff. That is really bad with anything more than 1/2" diameter differences.
Torsen does no build up heat like viscous coupling. It would even release the tension when you change state between acceleration and declaration. Old Toyota AllTrac also use viscous coupling.
I am running 255/80R17 that rotate 628 times per mile. My spare is 255/75R17 with 649 times per mile. 3.3% differences to axle differential. It's half that to the center diff. So 1.65% when both tire are new. Might be 0.5-1% at the most now. Putting it in front would make it even less since the front always travel smaller radius than the rear.
So small difference are OK. Obviously if you run 35-37 technically you do need full size spare, but I seen stranger things. Some don't even carry spare anymore with that size tire due to size constraints.
Torsen does no build up heat like viscous coupling. It would even release the tension when you change state between acceleration and declaration. Old Toyota AllTrac also use viscous coupling.
I am running 255/80R17 that rotate 628 times per mile. My spare is 255/75R17 with 649 times per mile. 3.3% differences to axle differential. It's half that to the center diff. So 1.65% when both tire are new. Might be 0.5-1% at the most now. Putting it in front would make it even less since the front always travel smaller radius than the rear.
So small difference are OK. Obviously if you run 35-37 technically you do need full size spare, but I seen stranger things. Some don't even carry spare anymore with that size tire due to size constraints.
