Originally Posted by gatorfast
Why can't he just replace one since the other tire has plenty of tread left?
I recently replaced only one front tire and my car rides just fine.
Because what we don't know is how the tire has worn. It may have 6mm of tread, but probably not evenly across the entire tire. I'm fairly certain that after 9k miles, there's some level of uneven wear. This is the main reason I always buy tires in pairs.
Obviously he can get just 1 tire, but I would at least make sure both are road-forced balanced.