So I opened the box MGP was shipped in, and there among all of the shipping popcorn was the game box. I immediately opened the game box and began punching out the tracks and examining all the stuff. When I pulled out the bikes, I figured out quickly that three of the six bikes were so loose they would not remain upright in game play, and the other three were well on the way to limpdom.
Then, I had a strange thought. What if I shoved a tiny piece of shipping popcorn styrofoam into the ball joint of each bike. It works. It works well. It creates the right amount of tension to keep the bike in any position you want.
I carefully separated each ball joint and placed a small piece of the foam (these are the white foam popcorn packing peanuts that you can squeeze and pop, not the off-white ones that simply get smaller in size when you squeeze them) inside the opening of the top side of the joint, and then carefully pushed the joint back together. You need to be careful, though. One of the clear plastic joints came out of a bike, and I'm not sure if it was glued in or not, so I just pushed it back in. We have played the game three times and all of the bikes work really well.