#TreadSeparation

Jimmy writes:

Sajeev,

For years I traded in my Hondas and Toyotas within 18 months of purchase. However, I did not care for the newest Highlander, Pilot, and Camry, so I kept the old ones hoping the next versions would be more acceptable. While I have not had a single problem with these vehicles, with the exceptions of a few light bulbs, I’ve noticed Michelin Green X and the Continental ContiProContact have small cracks in the tread grooves. The tires have 40,000 and 55,000 miles on them with lots of tread left. I have asked tire stores and some say don’t worry while others say they are dangerous.

What is the rule for tire replacements when it comes to cracks in the tread grooves?