Because used tires almost killed me!!
I'm tooling down freeway doing about 70, and I get a funny vibration, and then the whole truck ('57 Chevy) goes sideways, which then starts spinning. I end up sliding off the road into a ditch! When I left the road the truck started to feel like it was about to roll over, but it didn't, and I came to a stop a few feet from the fence. I thought I was gonna die!!
Turns out most of the tread on the left rear came off the case of the tire in one long strip. I picked it up! Luckily, one of my buddies Dane happened to be going my way, so he stopped and helped me out. We got it dragged out, and I was able to creep it home.
Want pictures?
Wreck #1 Wreck #2 They were used tires that had no dry rot, gouges, or cracks.