There are several different ways you can widen the wheelbase of your BCS walk-behind tractor.
One approach is to use wheel extensions. These come in various sizes that allow you to widen the wheelbase by anywhere from 4 inches up to 22 inches.
A different approach makes use of the two piece wheel design of most BCS wheels. The video shows you how to configure the inner hub up to four different ways to get different wheelbase widths.