<http://schema.org/description>
"Mountain bikes have fatter tires to give your bike a better grip on the trail. If you overinflate your tires, they could give you a bumpy ride. Underinflate them and they may tear. How much air should you use?"^^<http://www.w3.org/2001/XMLSchema#string>
<http://adventure.howstuffworks.com/outdoor-activities/biking/psi-mountain-bike-tires.htm>