To shift the drift a bit- Who here has filled their tubes (yes, remember those old school bladder things?) with some water? With a floor pump it's easy to remove the top cap off the cylinder, remove the piston and rod/handle, pour water in it and reinstall the piston then pump water into your tire. a few pump fills in both tires and then go ride it. Lot's of fun feeling the bike surge back and forth as the water sloshes about in the spinning wheels. Talk about un balanced wheels Or maybe the rider is un balanced. This is a fun trick to play on a friend too. Andy (who didn't forget to dry out the pump as to not corrode the check valve)