treadwear numbers vs mileage?

mscj

Member
Joined
Jul 24, 2005
I always thought a higher treadwear number pretty much meant longer tread life--then over the weekend I find a Michelin with a 420 rating and a Bridgestone with a 180......both state 60000 mile warranty. How can both be rated for 60k miles with such a vast difference in treadwear numbers?
 
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