[IsaacCarlson]

I have had no trouble with the beads collecting rubber.

Since the balls balance the tires as you drive, there is no critical speed. They start working at ~12 mph and stop at ~8 mph. If you are getting vibration, you have a worn part, incorrect weight in the tire, or a lot of lateral imbalance. I have traced all vibration to worn parts or a defective tire when the correct amount of weight is used.

As for wear, the rim is just fine, but the bb's lose their copper jacket in the form of dust and small flakes. This could cause some imbalance, but it is less than .1 oz, so most likely not. Either bb's are not round before the copper is put on, or they wear down from rubbing on each other in the tire when at low speed. They were round, but had a small nub or point on at least one end. I want to say it was from manufacturing, but I have no basis for that reasoning other than there seems to be a factory seam directly between the nubs on every bb.

It is amazing how fast those little balls are spinning at 10 mph before sticking to the tire. 19,000 rpm! That is, if they are truly rolling inside the tire and not bouncing.

We will see how the plastic bb's do. I have only seen rust on bb's that were in a tire with a bit of water for more than a few months. The dry tires had no rust on the bb's.