foam wheels

http://www.ebay.co.uk/itm/3307516820...%3AMEBIDX%3AIT
i am planning to order a couple of sets of these motors but im looking at some foam wheels on ebay :

http://www.ebay.co.uk/itm/2212163738...%3AMEBIDX%3AIT

theese ones to be precise and i am curious as to what size to order i think 3 inches is a bit big but i dont know how small will be too small for an invertable pusher

any sudgestions from previous experiance would be deeply appreciated

Probably you should be going with a 30mm body height beetle. So 45ish wheels are probably an idea. I've got some of these http://www.technobotsonline.com/fing...m-pk-of-2.html for low bodied robots and some of these http://www.technobotsonline.com/fing...m-pk-of-2.html on my spinner.