Here you go Mr. Know It All "Described simply, a tankslapper is rapid oscillations of your front wheel, casued by a bump in the road that suddenly gererates lots of energy. You may get a 'slapper landing a wheelie crossed up or by gassing hard over some painted chevrons, cats-eyes, or just down a bumpy lane. The sheer viloence of a slapper makes it difficult to know what to do. Initially, the things you SHOULD NOT DO are important. You should not try and control the slapper with your hands - your reactions are too slow and may amplify the furious flapping. Tensing up only makes the a tankslapper worse, as there's no way your arms can soak up the forsces quick enough, and you may end up making the oscillations worse. Braking isn't a good idea either, as the last thing the front-end needs is more weight on it. Off-road experience helps becasue gassing a bike through the slapper, thereby transferring weight to the rear of the bike, to the point at which the front wheel is lifted off the ground, is the tried-and-tested method of escpaing. After its all finished, make sure to pump your brakes because there's a strong chance that your pads will have been knocked out of their calipers." Taken from "How to attack panic", an article from Fast Bikes magazine.