Using a "rough" estimate by measuring with a piece of plastic and comparing it to a yard stick with 1/8" increments, I'm guessing at 10,000 miles I still have 9/32 of tread in the middle. I'll continue to look for something better to measure with.

It will be interesting too to see if the tread wears consistantly throughout the full depth. I don't have to worry about weather and hardening of the rubber because I'll be lucky to get more than a year the way I'm racking up milage.