Re the Greenball Transmasters.....our '07 HTT came with them OEM. Don't know if they were ever known as Towmasters. At about the 4 year mark we started shopping and decided that since the OEM gave us perfect service, we'd go with them again. At that time, seems we had to order online, but can't swear to it. Again, nearing the 4 year mark and a long trip planned, we decided to go ahead and have the peace of mind of new tires. Lots of looking. DH called the Greenball folks and was told that the Transmasters are now sold at Sam's Club. Went with them again, took our trip and then decided to move to a TT.
FWIW, when we were shopping the second time, I posted a couple of questions and mentioned the dreaded "budget" word, since we really hadn't planned on that investment right then. There were a few members who felt the need to eat me alive for considering "budget" and that "we might as well just get the cheapest possible and weren't considering the lives of our family". Strongly suggest you don't mention that word...guess not everyone has to have one of those plans. In any event, we had totally perfect service with the 2 sets we ran 4+ years each as well as the last time we heard from the owners of our HTT, they were also 100% pleased and no problems. Seems like the price was right about $100 ea at Sam's. I would not be concerned about those tires. DH was vigilant about checking pressure and torque before every trip and daily on longer trips.