We have some forklift tires on our poop-scraping skidsteer, they have 1700+ hours on now and still have a quite a bit of life left. They don't stop flats from hitting the curb, however. When they do finally wear out, my next set is going to be a set of the no-flat style made by McLaren, local JD dealer told me they would cost about $3400 for a set of 4.

Edit-a link, I hope: http://www.mclarenusa.com/nu-air/nu-air-semi-pneumatic-tires-for-skid-steer-loaders-and-backhoes.html