Smallest rubber wheel that can be turned by a technic axle What the smallest rubber wheels that can be turned by a Technic axle?

This is what I have so far



Wheel Full Rubber Balloon with Axle hole #4288

Background: I'm building a GBC and I want to push the balls at speed across an open area. I plan to hide small spinning wheels in the opening they go through and assume that rubber tyres are the best solution.
I think the smallest one in diameter is the tire 3641 



with the bush 4265c.



Alternatively, you can use the tire 3139



which has a smooth surface and also compatible (but a little bit loosely) with the same bush.