Everyone who’s been riding and experienced this phenomenon has feared this unexplained, uncontrollable wobble. Speed wobble, head shake, death wobble and shimmy are different terms used for the same action of a ‘tank slapper’. But what is this tank slapper and what causes it.
Well in simple words Tank slapper is an uncontrolled wobble of your forks and handlebars from side to side. And what causes this? Let us see…
A single-track vehicle has a tendency to travel in a straight line and stabilize itself, unless it is banked or leaned over. Which means a motorcycle being a single-track vehicle has to have both its wheels (front and rear) aligned straight, unless the motorcycle is leaned over. If you turn the front one side or the other the bike WILL turn and lean no matter what.
Now imagine you popped a wheelie and the front wheel is off the ground and when it lands back on the ground the front is not aligned with the rear due to riders input on the handle bars. At this moment your bike is upright, but the front is not in the same straight line. Naturally the bike would want to go straight or lean. So the bike pulls the front hard to get it back in line with the rear. This causes the front to have too much momentum and sling past the straight line to another side, causing it to wobble side to side, again and again, like a chain reaction. The even happens when you lose traction of the rear wheel for a brief moment.
Tank slapper can be caused by multiple things. It can either be your fault or the motorcycles. It can happen if the front suspension and its rebound is not set right. Or if the rear suspension is too stiff. But it all boils down to wheels coming out of line.
The wobble can sometimes be stopped and sometimes you can’t. The best way to avoid a tankslapper would be keeping a loose grip on the handlebars. Holding the handlebars tightly while riding puts in too much unnecessary input from the rider to the motorcycle. But if you’re unfortunate and you do face a tankslapper, keep in mind not to tighten your grip on the handlebars. You will only add to the wobble’s momentum making it worse. The best option is to drop the throttle and slow down. And if you’re still unable to save it at least you won’t go down that hard.
Check out the videos below.