Tires: tire wear, country tire, t grip

Question
about how much of a tire is worn off in one tire rotation?

Answer
Michael,

First the caveats:

Most tire wear occurs in cornering, so the miles a tire will get is not directly tied to miles it is driven.  A vehicle that spends most of its travel in the city will not get as good of mileage as a vehicle that spends most of its travel in the country.

Tire wear is also dependent on tread compound.  Some compounds are designed for grip and don't wear as well as tread compounds designed for wear - which don't grip as well.

But if we neglect all that and assume a tire gets 40,000 miles, is 30" in diameter, and starts with 10/32 of tread depth, then about a billionth of an inch is worn off every revolution.