pic: Nah, We just have a set for the Alpha bot and the beta Bot

[Kevin Ray]

thefro526, you hit it on the head. We have two bots and two wheels on each module. We went with the two wheels only because the drive shaft leading down to the bevel gear comes down on the side of the wheel and creates unnecessary stress on the horizontal shaft. By sandwiching the bevel gear we equalize the downward force.
As for the traction, it's simple physics. We neither gain nor lose traction. We especially like that they swap out easily and will bring the 4 beta bot spares to the competitions--hopefully unnecessarily.