Um, what causes this?

depends alot of times you can get 60-70% tread on a good used tired at a third of the cost just got to be friends with a few tire guys.
I also use to run um pretty low on the trailer then get um regrooved i still like that more then craps not sure i just never liked um
'on a regrove you can get all the trailer done cheap and get 40k or so more miles unless your a spread

 

Well, I did say pickup truck. With the cost of TT tires, I'd do used for my trailer in a minnit if I could get enough tread. But on the pickup I really noticed how I stopped having flats, got way more miles off a new one than two or three used, and I'd get the better ride and handling for the first half-life.

 

I just love it when the "industry" says the retreads are just as good as virgins now, I say well fine, you own the truck you put whatever you want on the hubs but I've learned my lesson