Tires: Two new tires vs. four, awd cars, subaru forester

Question
I drive a 2003 Subaru Forester.  My front tires are worn out
and need replacing.  The tire dealer (retail chain) is telling
me I must replace all four.  Is this legit?  Why do you think
the tire dealer is telling me this?

Answer
Bruce,

In your owners manual is a statement to the effect that all 4 tires need to be within - and I forget the exact figure, but it's something like - 1/4" in circumference.  If you don't do that, the center coupling could fail - very expensive.  The only way to be assured that the tires are within that dimension is if they are all the same size, make, model, and state of wear.

This is especially true for Subaru's which are known for this type of failure.  Other AWD cars and truck are less sensitive, but the advice to replace all 4 tires is good for those as well.  4X4's, too!