Seat has to be a minimum of 13" from ground. The bottom of the seat can be lower than the tops of the fenders, even lower than the tops of the tires. Look at the pictures in the 2014 rule book. The seat pan has been lowered below the tops of the fenders and actually sits even with the tunnel. If the tires are 16", and minimum seat height is 13", then the seat can actually be lower than the tops of the tires.