Tank Slapper

R

Roy Kjendal

#1
Would like peoples experience ans opinions and facts about:
What causes a tank slapper?
Once initiated can it be controlled or stopped?
Do they generally end catastrophically?
Are there any circumstances or bike configurations which tend to favor them?

Thanks for any and all responses
Roy
 

Tep_52

Premier Member
#2
Normally a tank slapper is caused by the front end getting light whether from acceleration or loading. When I raced dirt bikes the rule was when in dot throttle out, but that does take determinat ion and training plus sheer acceleration. And you just might make it. On the road I can't say that I would recommend this as I always find it better to wreck at lower speed better than high speeds unless you just have a ton of luck and or talent. With that said I have saved tank a tank slapper in the past but it did required a change of shorts.
 

Garry in AZ

Premier Member
IBR Finisher
#3
What causes a tank slapper? It's a type of harmonic oscillation, usually caused by your front tire hitting a bump, or a series of bumps at a specific frequency. It happens more often when accelerating, and there is less weight on the front tire.
Once initiated can it be controlled or stopped? It's difficult to control, but if you can relax your arms and shift your body weight forward onto the tire, it can help significantly. Rear brake application apparently has also helped, but I have not tried that. On high horsepower bikes, a big handful of throttle will lift the front end enough to get it off the ground, and it will also stop the oscillation. But you have to be pretty brave to deliberately accelerate an already out of control bike.
Do they generally end catastrophically? Much depends on the severity of the shake, and the experience and skill level of the rider, but I'd say at least half the time, they don't end well, usually because the rider freaks out and gives up trying to control the bike.
Are there any circumstances or bike configurations which tend to favor them? Bikes with lots of power, being ridden aggressively out of rough turns, bikes with improperly adjusted steering head bearings or steering dampers, bikes with misaligned wheels and/or bad swingarm bearings, and every Honda 305 Dream I ever rode. Those bikes handled like there was a hinge in the middle of the frame.

Garry
 
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rodneyw71

KLR'er
Premier Member
#4
I've had the death shake start to happen while going down the interstate on my klr, I was passing a semi and my front end just started to slowly shake, the whole bike just felt like it was going to start shaking, I just eased out of the throttle and when I got away from the truck it stopped, I don't know if it was the wind or turbulence, but I almost needed a new beadrider after that one, I'm going to be putting a front stabilizer on it soon, so hope that'll help it.