| Member |
 Discussion Topic  |
|
|
dogdoc427
 Standard Member
192 Posts
Milan, New York
USA
Yamaha
650+87 Honda GL1200I
|
 Posted - 09/08/2009 : 8:51 PM
|
I am aware that a tank slapper can happen on any type of motorcycle as James has made clear. My question is: Is any type of bike (sport, cruiser, standard or chopper) more or less likely to experience a tank slapper?
I am aware that proper steering head and damper adjustment is essential to avoiding one, I am just curious because I have been told it was "common knowledge" that "it CAN NOT occur on cruisers". A statement that I understand is false.
Regards, Dogdoc427
|
|
|
gymnast
Moderator
2814 Posts
[Mentor]
Meridian, Idaho
USA
Harley-Davidson
Sportster Sport
|
Posted - 09/08/2009 : 10:27 PM
|
| Dogdoc427, the statement is indeed false and the person who said that a tank slapper cannot occur on a cruiser is apparently not aware of such occurrences that have been detailed or recounted on this website involving cruisers, sportbikes, and standards. Your understanding of the falsity of the "common knowledge" statement is correct. |
 |
|
Niebor
Ex-Member
|
Posted - 09/09/2009 : 7:57 AM
|
| I'd assume my FXD counts as a cruiser to about anyone. Personal experience says they can indeed experience a tank-slapper. In my case a slight road blemish combined with a loose headset bearing made for a nasty afternoon. |
|
|
|
dhalen32
Moderator
644 Posts
[Mentor]
Omaha, NE
USA
Buell
XB12X Ulysses
|
Posted - 09/09/2009 : 8:38 AM
|
DD427:
Steering geometry plays a great part in a bike's tendency to have the bars oscillate back and forth in what you have called a tank slapper. All other things being equal, a sport bike's steeper rake (closer to vertical) and shorter trail will be more likely to start this scary oscillation than a chopper with more shallow rake and longer trail. Typical cruiser and standard bikes' steering geometry will generally land somewhere between these other two bikes' extremes.
Many of today's latest sport bikes come factory equipped with steering dampers to prevent unwanted high speed steering oscillation. Some are even electronically linked to the speedometer to increase dampening effect as road speed increases.
However, as you have been told, any bike can experience this problem given sufficiently worn steering head bearings, underinflated front tire, defective front tire, etc.
Dave
|
|
|
|
Arnold
Junior Member
87 Posts
Chicago, IL
USA
Kawasaki
KZ1000
|
Posted - 09/12/2009 : 12:56 AM
|
Make sure your wheel is in balance is your first line of defense.
If you are on a cruiser and experience a tank slapper you need to get the weight off that front wheel or you will be facedown in the asphalt!
The best way is to either jam on the throttle or if you are more skilled you can downshift a gear, jam the throttle and pop the clutch out. Either way you need to get that front wheel as near off the ground as safely possible. |
|
|
|
James R. Davis
Administrator
14935 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
|
Posted - 09/12/2009 : 8:07 AM
|
This is EXTREMELY DANGEROUS advice.
My recommendation is just the opposite - to change the front-end geometry by applying your brakes as quickly as possible (not as in grab a handful, but as in emergency stop). This loads the front-end with weight and dampens the tank slapper (OR NOT), but at least slows you down in the event that you do have a get off. |
|
|
|
gdickelman
Moderator
1191 Posts
[Mentor]
Annandale, VA
USA
Moto Guzzi
California Vintage
|
Posted - 09/12/2009 : 8:36 AM
|
quote:
Originally posted by dogdoc427
I am aware that a tank slapper can happen on any type of motorcycle as James has made clear. My question is: Is any type of bike (sport, cruiser, standard or chopper) more or less likely to experience a tank slapper?
I am aware that proper steering head and damper adjustment is essential to avoiding one, I am just curious because I have been told it was "common knowledge" that "it CAN NOT occur on cruisers". A statement that I understand is false.
Regards, Dogdoc427
The answer is a simple matter of physics. Any two wheeled vehicle with a steering head can experience the kind of resonance that results in a tank-slapper. It is an oscillation of the front wheel (the one associated with the steering pivot) resulting from an outward acceleration of that wheel. For example, a "wheelie" (or weight reduction on the front wheel), followed by restoring that weight AND adding an outward acceleration on the wheel initiates the oscillation. The natural "righting" (or "restoring") force causes the wheel to accelerate in the opposite direction, and the process simply repeats. If there is insufficient dampening, the oscillations get larger, and there you have it.
As long as there is enough freedom in the steering head to properly steer a motorcycle, there will be some probability of a tank slapper, under the right circumstances. Steering dampers, proper adjustments and riding habits (like NO WHEELIES) reduce the probability, but never eliminate it completely. Simple physics.
How do you stop a tank slapper once it starts? Good luck! Bottom line is that the dynamics are such that the rider does not have the means (or the time) to eliminate the outward acceleration of the wheel at any given oscillation. I have heard things like "drag the rear (with the rear brake)" or "hit the front brake" or "aggressively 'clamp' the handlebars" or "lift the front wheel" - but each of those things is a crap shoot. There is a very small probability (minuscule) that the outward acceleration of the front wheel will be canceled by one of these things. But probably not.
As James suggested, at least try to slow down to mitigate the consequences of dumping. |
|
|
|
dogdoc427
Standard Member
192 Posts
Milan, New York
USA
Yamaha
650+87 Honda GL1200I
|
Posted - 09/12/2009 : 10:24 PM
|
My thanks to all. As I stated I was curious as to whether or not one type of bike is more or less prone to a tank slapper. While I had the bike up on the jack to do the tires I went through the check and adjustment procedure for the steering head and it was in spec. so I am not too concerned about it.
The curiosity arose when I asked my dealership about the cost of a damper to fit the V-Star. They basically looked at me like I had 3 eyes and said "Why? It's a cruiser! It can't happen to them." My attempts at enlightening them were futile at best, they've been selling bikes for so long they feel they have all the answers. I pointed them to this site in hopes they may learn.
Regards, Dogdoc427 |
|
|
|
scottrnelson
Advanced Member
5262 Posts
[Mentor]
Pleasanton, CA
USA
KTM
990 Adv, ST2, XR650L
|
Posted - 09/14/2009 : 5:41 PM
|
I experienced a tank slapper in 2003 and have written a few things about it on this site. In my case, it came on so quickly that there wasn't much I could do about it. I certainly couldn't do anything with any of the controls on the handlebars.
There are a few specific motorcycles known for a higher tendency to have tank slappers. The early Ducati Monsters were one such bike, with a 23 degree rake. I think the Suzuki TL1000 also was known for that. A good steering damper helps considerably for those bikes.
I wouldn't bother trying to put a steering damper on a V-Star, though. |
|
|
| |
Discussion Topic |
|
|
Most Recent Posts
|
Activity History
|
Safety Tips
A question about tank slappers