Tank Slapper, My First

[ethics]

Not sure why they call it Tank Slappers since it's more like shimmies but had that this morning. It was over before I even had time to get all crazy about it. Maintained throttle, and it was no big deal.

I REALLY need the damn dampers. ;)

[Sierra Mike]

Wow, those are scary...had it once and wound up on the deck.

SM

[ethics]

Happened too fast for me to crap my pants. :)

[BigDeputyDog]

What’s a Tank-Slapper?
A violent oscillation of the front steering. All steering systems on motorcycles have a natural frequency (or speed) where, given an initiating disturbance, they will tend to oscillate quickly from side to side, each oscillation bigger than the previous. At its worst, the steering will be hitting the stops very rapidly—thus the term “tank slapper.” Damping prevents this from happening, by the rider’s arms and sometimes helped by a hydraulic steering damper. The newer sport bikes with their steeper steering geometry are more susceptible.
The most common slapper scenario is to be accelerating rapidly from a corner over broken pavement where the front wheel is barely touching the ground. A combination of bumps in the pavement and the rider attempting to steer the bike while the front wheel is slightly off the ground can cause an initial disturbance that is exactly at the natural oscillating frequency of the steering and overwhelm whatever damping the rider or bike is providing. Most people, however, seem to be able to ride them out.
Of course, worn steering bearings, worn tires, accident misalignment, poor suspension setup, etc. can all make the bike more susceptible to this problem.

A very good source (http://www.timberwoof.com/motorcycle/faq/riding.html);)


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BDD... :{)

[ethics]

LOL! That's the worst case scenario! BTW and OT, that racer is shimmying because of his rear suspension "popped". I saw the whole documentary and this was part of it. The guy never raced again after this.

[cmhbob]

I always called it the "GoldWing Wobble." Never saw it on my Harley or BMW; just the Wing.

[ethics]

I wonder why that is?

[Violet1966]

Why did it happen to you Leon? Any idea? Scary. :(

[ethics]

Making a lean curve hwy turn, hitting nasty tarmac holes, the usual suspect with these. I was doing about 70 too so it was over pretty fast. :)

[Violet1966]

Well thank God you kept it together and hope it never happens again.

[ethics]

Hehe, I am just glad I didn't automatically react negatively. I just was like, "this is weird..." and then it was over. Reflecting upon it was like, "holy crap, wtf was THAT!?!?"

[Biker]

When I was first putting the sidecar on the old Yamaha, I took it out for a test run without the steering dampener to see if I had the chair aligned properly. At 25 mph, I developed a front end wobble that was so bad, I thought I was going to tear the mounts loose. Shut the bike down and almost walked back to the house. That was a definite case of first you say it, then you do it!

[cmhbob]

Dunno - was pretty weird. Only happened in a particular speed band (usually around 28 - 32 MPH), and only decelerating. Saw it in a 99 GL1500, as well as several GL1800s, but not on the Valkyries, and not on my 97 GL1500. I was told it was a Goldwing thing, and to get used to it.

[Biker]

I wonder why that is?

Usually has a lot to do with the tire your using along with the fork design of the bike. One of the reasons I always slap on the best quality tires I can lay my hands on.

[Brazbit]

Dunno - was pretty weird. Only happened in a particular speed band (usually around 28 - 32 MPH), and only decelerating. Saw it in a 99 GL1500, as well as several GL1800s, but not on the Valkyries, and not on my 97 GL1500. I was told it was a Goldwing thing, and to get used to it.
Strange I never had anything like that on my 1100 or my dad's 1500 when I rode it. Heck I have taken my hands off the bars and all three bikes always tracked true. I have however observed this on a twelve speed bicycle before.

[MNeedham73]

I think I'll just count myself lucky that the only thing that has gotten the front tire of my bike acting funny is the damn pavement crack sealant on most of the roads around here. Get the front tire on one that runs down the road and my bike gets a little wiggly :)

http://arnoldasphalt.com/images/harleyb3.jpg

[ethics]

Ooooh, watch those in the rain, they get extra jiffy lubed slippery.

[MNeedham73]

Yeah, I've noticed :haha:

[Kluge]

The highway people tried machining the road surface of route 495 near here (by exit 67, police HQ) to get rid of washboard slabs in a new and different way, and their machine somehow altered the tracks where car & truck tires ride. If you can imagine a really huge half-pipe like the skateboarders play in, then trim it until you can't see the reverse camber like 1/64 pipe or 1/128 pipe or whatever, and put two in each lane, I think that's what you get there.

The reverse-camber geometry of the surface is opposite to the stabilizing geometry of a bike or car, and that stretch of road feels funny as if you're in stiff crosswind or maybe have an under-inflated rear tire. I haven't heard of any accidents or publicity about it, though, it's mild enough so you aren't sure what it is until it happens day after day in the same place. I'm not even sure about the direction of the reverse-camber, I think the shallow pipe is the one that would do it.

[SixofNine]

In this video the guy gets out of it:
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In this one the guy doesn't, but don't worry, he recovers and he has a cute girlfriend to boot. :)
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[ethics]

Jeez. I doubt the dampener would have helped there!