[GeeTwo]

We use pneumatic wheels for our t-shirt cannon. Our chassis is AM 31" nanotube (27.5" wheelbase, 6 wheel, with 1/8" drop) using Harbor Freight pneumatic wheels with the bearings removed and replaced with bushings for keyed shafts. Don't do this! The scrub is pretty bad, as we can't get the bushings in tight enough to get rid of the wobble. We're upgrading to AM pneumatic wheels and hubs this summer. Between the more solid hubs and slightly underpressuring the corner wheels, we figure we can make a much more nimble robot. Time will tell; if this doesn't do it, we may have to modify the center axle to lower it a bit more or replace the nanotube frame.

As far as pneumatic wheels, I definitely recommend them over solids; much less likely to tear up grass and race track surfaces due to the larger area of coverage.