I have 2 tires that have 70% tread. And 1 tire that has 50% tread. Initially I was going to use the 2 70% tires and buy 2 new tires for the rear. On another forum guys seemed to think I would be fine using all 3 used tires and buying only 1 new tire. FYI this is going on a solid axle RWD. Any opinions?

 

If 2wd, there isn't likely going to be a problem. Go ahead.