15/32" isn't much tread depth to start out with for the snow country. In California, Nevada, and Colorado when the tread depth gets below 6/32" the tires aren't legal for snow traction on their highways. In Colorado the law begins on September 1st each year and lasts for some 8 months through May 31st.
Never mind the tire warranty due to I tossed my Cooper S/T Maxx tires when they hit 41,000 miles and they all had a 5/32" minimum tread depth left. There was plenty of dry pavement mileage to run on them. The High Country ain't Kansas due to the winter weather can be Arctic conditions at the higher mountain passes. The set of 35" 3PMSF tires that I just installed are 19.3/32". A 4.3/32" deeper tread depth than the Maxxis to begin with. In addition a deeper tread depth is better in getting you through deep snow.
That's the complaint too on this Power Wagon forum with the BF Goodrich KO2'S being that they start out with only 15/32" and won't last as long versus a comparable brand of tire with a greater tread depth when new. The PW is a heavy truck and needs a deeper tread depth to begin with. The stock new Duratrac tires on it had a deeper tread depth than the Maxxis. So did my S/T Maxx.
