[edthegeek]

We did that for our 2005 bot and for our 2006 bot(even though it was a 8 wheel drive). We lowered it about 3/8-1/4 inch, It was variable. We did this not by making the center holes lower, but by making bearing blocks for the back wheels ,which had slots. Therefore, the assembly was adjustable. This allowed us to adjust how quick or how unstable the chassis was when turning. For tread, we used SBR rubber (its the stuff that makes the soles of your tennis shoes). We also got it at McMaster. Our wheels were made out of milled 6061 Aluminum. To hold the rubber in place, we used Loctite 404. Loctite 404 was designed to glue drag racer tires to the hubs. However, I recommend against using the glue because it can be temperamental and result in the rubber peeling off. A better solution is to use pop rivets to hold them in.