I've always ran re-treads on my road tractor (except for the front), and I was wondering if you guys usually buy new or use re-treads? I've got a tandem with 11R 24.5 radials. The price difference is around $100 per tire, maybe even a little more if I give the re-tread place some old casings. I usually replace the tires two at a time. I just didn't know if there is any advantages/disadvantages with either kind? I haven't had any problems with the re-treads coming apart or anything, they just wear down. I didn't think the life span (tread) is longer on a new tire though. Any thoughts?