I have a 2005 Subaru Legacy 2.5i Wagon.
I just destroyed the passenger-side rear tire.
The tires have approx. 6/32" tread remaining, per an informal measurement with a coin (I used this guideline from tirerack.com)
These are Nokian tires, and according to the specs I found online, they have 11/32" tread depth when new.
Another article on tirerack.com on this topic, suggests that Subuaru states that the differential among tread depth should vary no more than 2/32"
My owner's manual does not specify the what difference in tread depth tolerance is, however they do point out that I have a dashboard indicator "AWD" that will flash if the vehicle is driven with tires of different diameters, and I assume, the drive train is in danger of being damaged.
Among my family and friends, I've received conflicting opinions regarding whether I should replace all 4 tires immediately, or if I could potentially purchase the same brand and model of tire, whose tread depth, I assume, would be 11/32" and be different by approx. 5/32" from the existing tires.
Does anyone have a definitive answer as to which option I should choose?
Is it true that tread-depth can influence tire circumference enough that driving my Subaru for an extended period of time would damage the drive train?
CONCLUSION: I chose to replace all 4 tires with new tires, and I'm happy I did.