Tank Slappers

[battlecry]

Moto-science is right.  Weave mode oscillations are poorly damped or unstable at high speed.  Wobble is poorly damped or unstable at mid-range of speeds.  It is the nature of the two wheeled beast.  It is only a matter of time until you find the combination of vibration mode, speed, and ground excitation.  When you find it, it may be over before you know it, so a continuously acting damper makes sense. 

I even had a tank slapper on my Vespa.

My first purchases for my Monster were the 14 tooth front sprocket and the damper.  I'd do it again.

[Drunken Monkey]

My advice to folks is that if you have a persistent wobble, you should look into getting it fixed, not look to mask it with a steering damper.

Beyond that, a steering damper is good insurance from a nasty confluence of just the right input on the wheels, suspension, frame and your arms to cause a tank slapper.

Personally, I've found most wobbles can be cured by tuning your suspension properly and making sure you're not putting to much pressure on the bars.

And lighter wheels help as well, but that's an expensive way to fix a wobble.

[Bill in OKC]

If you ride fast twisties on your Monster, a damper is a nice investment/insurance policy.   You see factory dampers on the high-end Ducs.  

[scott_araujo]

that would be a great argument if it wasn't a bonestock 99 Monster that I had my slapper on.

Raux, I should clarify.

As a safety catch when you run into an unexpected road hazard like you and science did, sure.  If you want one install one.  I agree, it may save you in a situation like that where the bike or your skills might not. 

What I object to is people installing one as the first fix for a wobble.  If your bike wobbles/twitches/wiggles on smooth pavement when going straight or around a steady turn you should find out why it's doing that and sort the problem out.  A steering damper can mask it but won't fix it.

Scott

[Moronic]

IMO it is mainly about suspension, especially on a bike with fairly conservative steering geometry such as the Monster.

I doubt it is a coincidence that both reports above of serious tankslappers arose after the bike's front wheel hit a very sharp and very hard step in the road surface.

Many years ago I had the use of a Yamaha FZR600 (not sure what they were called in the US), which was prone to violent tankslappers in straight-line high-speed travel over certain roads that were moderately bumpy. After fitting firmer fork springs from Ohlins, some damping oil that worked with the springs and an Ohlins shock, bike became perfectly stable at same or higher speeds on same roads.

Of course, fitting a steering damper would have been cheaper than sorting the suspension.

What I am not so sure about is how effectively a typical steering damper will resolve the problem. Can also recall riding a Suzuki TL1000 that had a std steering damper. No head-shakes but at one point it did get into a horrible rolling wallow after hitting a few bumps cresting a rise at 85mph or so. Felt like the bump-crest combo upset the suspension and the steering damper was doing its best to cope - only best was not very good and for about 50 metres I was a mere passenger, not the rider.

Another anecdote: Honda's original Fireblade (1992?) had radically sharp steering geometry for its day and no steering damper. People predicted fearsome headshake issues on bumpy roads. Bike went on sale and everybody reported awesome stability. But that first model, if not all which superseded it, had very good stock suspension.

[moto-science]

I stand corrected....Howie. Ducatis have used  23.5 - 24.5º rakes,
It the Buell that uses a suicidal 21º rake. (RIP)

Now that we are in the CANBUS network era, the electronic steering damper
offered on the GSXRs is an excellent idea. Speed related active steering dampening.
We are still in the passive steering damping era, not sure how well the Hyperpro 'active'
damper works. Supposedly dampens harder the faster the piston moves.

The brutal truth is the more you ride, it is just a matter of time before
you go down. I went ~10 years without crashing and without a steering damper.
I ride 365 days a year and go without a car. My luck was certain to run out.
Crashing like that was a wake up call to improve my suspension set up and footwear.

A bad tankslapper is not a mere wobble, it is an instant lock to lock violent oscillation.
You break fingers from it before you even know it, there is no recovery from my experience.

[justinrhenry]

[kopfjäger]

...and this means what?

[swampduc]

...and this means what?

+1

[Aflac]

Here's a good write up on this issue from Shazaam on the ducati.ms site

http://www.ducati.ms/forums/showthread.php?t=35548

[Bill in OKC]

A bad tankslapper is not a mere wobble, it is an instant lock to lock violent oscillation.
You break fingers from it before you even know it, there is no recovery from my experience.

I cannot imagine using either the throttle or the front brake when it happens.  A friend's slapper pushed the front brake's pistons/pads out so that it took several pumps of the lever to get any front brake back after the slapper had gone away.  He nearly sailed through an intersection before he got them pumped back up.  That slapper had snatched the grips right out of his hands.

[LA]

I was a naysayer to dampers for a long time, but they do work and add a trivial amount of weight.  I use a side mt. Ohlins for the last 30k mi. now. Even my old 74 R90S came new with a very good hydraulic damper.

In "normal" riding you shouldn't need a damper. Light on the bars and controls is important.

Both the DS1000 and the S4R/RS lift the front end so easily in the first two gears and seriously unload the front if not pull the wheel when exiting corners under power in third. It's easy to add unwanted steering inputs with so little or no weight on the front end in that situation.

Bumps or serious dips at the apex of turns make dampers a very good idea IMHO.

LA

[RUFKM]

Related question:

Do light wheels like BST's increase the potential for a tank slapper due to the reduced inertia, or minimize the effects to a manageable level due to the reduced inertia?

[kopfjäger]

Related question:

Do light wheels like BST's increase the potential for a tank slapper due to the reduced inertia, or minimize the effects to a manageable level due to the reduced inertia?

My guess, and purely a guess would be they would minimize the problem. As was stated before, proper suspension set-up is key (most folks never do this), as I have found with my wheel/brake set-up which is lighter than just a set of BST wheels. On another note. I have not seen a race bike without a damper. ymmv

[Desert Dust]

My worst experience with a front end wobble (borderline tank-slapper) happened about 37 years ago, when I was about 18 years old. I was going about 85 MPH on a Honda 305 down a smooth highway. The handlebars began shaking violently; all I could do was hang on and back off the throttle. I finally got the thing slowed down and pulled safely over to the shoulder. My underwear had to be disposed of. 

Obviously, the bikes most of us ride today are far superior to the beasts I was born on, but the fact that I can recall this incident as clear as if it were yesterday makes me realize I don't want to experience anything like it in the future.   

  Considering moving steering stabilizer to the top of my mod list.