13. I've gotten a lot of questions about the Parnelli Jones Dirt Grip tires (that you can pick up at National Tire and Wheel or Desert Rat, by the way). So far, they have been excellent. I am wearing them out a little faster than I'd like to, but there is still a lot of life left on the tires. They've worked well in the rain on the highways and get excellent traction in the mud and snow for such a nicely-driving street tire.