I agree, buy 8 ply if you can find them. Denman Tire still makes them. Cocker tire has 12ply and Universal tire stocks 900-20 in round shoulder only 8ply. The 900-20 may of been a post war size as you can only find it with round shoulder. If you look at footage and photos from early WW2 the half-tracks and Trucks used a tread design that looked like a large v-tread almost like a Farm style tire. One of the reasons they started using the traditional NDT is because of the Rubber shortage. The NDT tires used a lot of vinyl and synthetic materials. They stated using synthetic rubber during the war and the Military style NDT used very little real rubber compared to previous tires. That is why they wear out so fast because the tread isn't very deep to begin with. The other poster is correct about the lowest bidder, however it's for the design not production cost. Over the years every major tire company has made these tires, Firestone, Kelly, Cooper, Goodyear, and so forth. About six months ago I saw a tire dealer liquidating an entire building of old tires in Union MO. I saw a hundreds, and I mean hundreds of Military tires being loaded onto a Trailer. Every size possible. I was told they were 20 to 50 years old!! I believe they all went to Independence MO and then to Mexico. Here are some links.
http://www.universaltire.com/truck-and-military/military/900-20-sta-military-ndcc.htmlhttp://store.cokertire.com/900-20-ndt-military-12ply.html
