tires
 

just perusing tire companies and found some interesting tread styles http://www.titanstore.com/store/agricultural.html titan has some interesting stuff and look at the treads on this wheelchair page...chinese made http://www.affordableoption.com/trea....html#K183-248

Yikes
 

It's a scary wheelchair that has tyres like this; check out the last two rows specifically:

http://www.affordableoption.com/images/tires/tread6.jpg