Sorry. I should have stated that my interpretation is for Xdrive cars when the diff is locked. Pre-xdrive cars will still overheat the diff with mismatched tires, but will tolerate a lot more RPM differential from one axle to the other before they have trouble.



Some old AWD racecars actually used viscous LSDs with slightly different sized tires front to rear in order to keep the viscous fluid hot enough. The Porsche 959 is one example.

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2003 3.0 5MT Topasblau
Purchased in 2016 and surprisingly still running