Depends on the AWD system. If there’s a center diff or a clutch in the center, the speed differences where the front axle and the rear axle meet can cause excessive wear and heat. Subarus are the most common vehicle for this, but some high end German stuff I know can have issues as well. But generally economy cars and midrange cars disconnect the extra axle or have a loose coupling to it, so only two tires replaced are fine.
Every certified Subaru mechanic and mechanics working directly for Subaru have always said I only needed two when one tire needed complete replacement for my Forester.
As long as they are within 1/4" diameter variance this is true, otherwise you FUBAR the viscous coupling over time. Which is why most mechanics default to ‘just replace all of them’.
Depends on the AWD system. If there’s a center diff or a clutch in the center, the speed differences where the front axle and the rear axle meet can cause excessive wear and heat. Subarus are the most common vehicle for this, but some high end German stuff I know can have issues as well. But generally economy cars and midrange cars disconnect the extra axle or have a loose coupling to it, so only two tires replaced are fine.
Every certified Subaru mechanic and mechanics working directly for Subaru have always said I only needed two when one tire needed complete replacement for my Forester.
As long as they are within 1/4" diameter variance this is true, otherwise you FUBAR the viscous coupling over time. Which is why most mechanics default to ‘just replace all of them’.