I have a 2010 chevy PU... I think I saw a spare one time when I was looking under my truck. I have replaced the original tires once.. but not the spare. does it need replaced at the same tine also???
At 10 years old, dry rot would be likely enough I would not rely on that tire for more than limping duty. Old tires don't hold up well to heat (i.e. load and speed over time).
