The additional groove is actually formed by an extra piece of steel welded into the wheel arch. This is to offset the unsightly gap that would be apparent when the regular wide 10" wheels are fitted to it. The rear suspension is also setup for 10" wheels, rather than 13", so I suspect there will be handling issues a regular Townace won't see. The smaller tires allow for a flat floor. In retrospect, the floor/ceiling height is actually lower than the regular version, but the advantage is that the flat floor can accept standard sized cargo pallets, which is the whole point of the exercise.