I attached these to my copal 50:1 motors, and they work great. They have a lot of friction, and provide plenty of traction for keeping my robot in the ring.

Probably the best wheels for ants or Beetles. The "Dave Hubs" are a great way of fitting them to a B16 motor

These tires are grippy and great. They squish so much, they actually absorb impact. The larger sizes aren't so useful, but the smaller size is perfect.