Originally Posted by wpmarky
Your tires need to be within .25" circumference of each other to prevent your diff from frying.
If you only replace 2 tires, the new ones will have less RPM's than your older tires since the circumference is bigger. Your open differential will sense that, and will try send power to the tires it thinks are slipping (rotating faster). Since your new tires will always be bigger, your diff will always be 'working', and may lead to overheating and frying your diff.
thanks for your explanation. thanks to the others too that replied. i also got a hold of my service tech at the and got pretty much the same technical explanation. he recommended that i go to a different shop that they send their cars to and they will measure tread depth on my other 3 tires and make their recommendation based on that. where as les schwab just told me i'd need to replace all 4 with either their house brand tire or some $1000 toyo tourevo's.