Buy new, combine tires are always overloaded, sidewall issues are common. Just do it, price them out, tire prices are down from a few years ago.I'll add this, I replaced all 4 of mine a few years ago, same size. Goodyear, one was ready to blow, glad I did it before it went.I went with FS Deeptreads, I like them.
Combine tires new or used.
