Discussion
Recently seen a couple of clips on the TV of motor cyclists caught out by a tank slapper at high speed which resulted in a very nasty crash in each incident. What causes the front of the bike to shake violently and is there anything you can do to retrieve the situation before the bike spits you off baring in mind that it is usually all out of control in a matter of seconds? Anybody on here escaped a tank slapper if so how? Cheers
JT
ugh, its a tough one..
tanks slappers are the result of geometry, the steeper the steering angle the quicker the bike turns, but the less stable it is. On a race track this is fine because its smooth, so there are less things to provoke a tank slapper, the people most prone to them are fast road riders, setting up the bike for best turn in makes it unstable, and more likely to slap under power.
a normal road bike with slightly more conservative geometry would be unlikely to slap on the road..
tanks slappers are the result of geometry, the steeper the steering angle the quicker the bike turns, but the less stable it is. On a race track this is fine because its smooth, so there are less things to provoke a tank slapper, the people most prone to them are fast road riders, setting up the bike for best turn in makes it unstable, and more likely to slap under power.
a normal road bike with slightly more conservative geometry would be unlikely to slap on the road..
You can get in a tank slapper on big triallies going at high speed or sports bikes with sharp steering. ALso from mis-matched tyres or white-lining as well as other influences.
Tanks slappers start with a wobble that rapidly increases to the point where you can no longer hold onto the bars.
The only chance of saving a developing tank-slapper is to grip the tank as hard as you can with your knees. I'm not sure of the logic of why it works, but it does.
Tanks slappers start with a wobble that rapidly increases to the point where you can no longer hold onto the bars.
The only chance of saving a developing tank-slapper is to grip the tank as hard as you can with your knees. I'm not sure of the logic of why it works, but it does.
Not had many, but I have had some. Most of mine started as a slight weave (although some happen when you bang the front down hard when you are not upright), and so should have been caught early enough to not develop fully. Keep a light grip on the bars (don't wrestle to keep then still), and gently back off the throttle, and it should calm down again.
Seems a much less frequent event on modern bikes with modern tyres. It used to be a pretty normal occurrence when pushing hard on 80s machines.
Seems a much less frequent event on modern bikes with modern tyres. It used to be a pretty normal occurrence when pushing hard on 80s machines.
Biker's Nemesis said:
FM said:
Backing off the throttle a tad always helps in my experience...
Backing off the throttle will in almost all cases, make it worse, I've been spat down the road at 100mph plus with a tank slapper.Edited by FM on Sunday 18th November 21:22
It did hurt.
I pull out to overtake two cars, shoulder check, indicators.
Car in front of me pulls out to overtake the first without indicating when I am level with it's rear bumper, forcing me onto the edge of the road.
I lift off to try to get behind it, the handlebars go crazy, i think I'm about to die.
Unfortunately my lifing off only suceeded in slowing me to the same speed as the overtaking car, thus pinning me on the side of the tarmac.
I reapply the throttle progressively, keep a tight grip on the bike, the bike stablises and pass both cars.
I go white, shiver etc etc and then express my displeasure at the car drive in the form of a hand gesture.
The big thing with a tankslapper is to stay with the bike (duh) so long as you are moving with the bike you can damp out the ocisaltions. The second you come away from the seat you will be a seperate mass to the system and instead of damping the motion you will add to it. (like moving your legs on a swing) I've seen Valentino Rossi get back a bike that has thrown him from the saddle but mere mortals are unlikely to be able to do this. Hence the advice to grip the bike with your knees.
To get technical, the tankslapper is caused by the front end losing grip ever so slightly, and regaining it at a different angle to the bike. imagine your back end was giving it some welly and you turned the bars to 90 degrees. the bike doesnt turn, the front end does. because this happens so fast, quite often the front end will move to far the other way (generally to full lock in the opposite directon) then it repeats, getting faster and faster.
I've had one caused by the front end lifting ever so slightly then hitting a cats eye. Although it seems insane, gas it. Lift that front end up again so you can regain control of the bars.
if you don't act quick you'll completely lose control as it gets more and more violent. Not pretty.
DONT TRY TO WRESTLE THE BARS INTO CONTROL! This will make it worse.
Hope thats of some help. If you get one (and survive it), fit a steering damper.
I've had one caused by the front end lifting ever so slightly then hitting a cats eye. Although it seems insane, gas it. Lift that front end up again so you can regain control of the bars.
if you don't act quick you'll completely lose control as it gets more and more violent. Not pretty.
DONT TRY TO WRESTLE THE BARS INTO CONTROL! This will make it worse.
Hope thats of some help. If you get one (and survive it), fit a steering damper.
I've had a few slappers 
over the years, luckily never crashed because of one but it is my understanding that easing off is the wrong thing to do, kind of like in a rear slide the right thing to do is the unnatural thing ie to power through it and above all remain calm & relaxed, don't tense up.
Steering damper should help control it, my 916, with damper, has never done anymore than a minor bar wiggle and even then only under worse-case conditions.
over the years, luckily never crashed because of one but it is my understanding that easing off is the wrong thing to do, kind of like in a rear slide the right thing to do is the unnatural thing ie to power through it and above all remain calm & relaxed, don't tense up.Steering damper should help control it, my 916, with damper, has never done anymore than a minor bar wiggle and even then only under worse-case conditions.
Uncomfortably...I`m still going to go against the grain on this one...on my last 1/4 mile session..there is bumps halfway down the strip...in the power it kept going into slappers consistantly all day unless I short shifted or rolled off ...it`s my understanding that the front wheel is just kissing the tarmac & is unloaded hence free to skip left & right over bumps ...less power means more weight on the front...I`m sure most have had the bars go mental accelerating hard over a rough road & it`s been my experience that the osscilations gradually increase unless you roll off...
I`m not naive however & know that there are different reasons for each tankslapper of course as described in the above post where the front went spastic when the rider shut off during the aborted overtake mentioned...
What ever works for the rider.
I`m not naive however & know that there are different reasons for each tankslapper of course as described in the above post where the front went spastic when the rider shut off during the aborted overtake mentioned...
What ever works for the rider.
Edited by FM on Monday 19th November 11:26
FM said:
Uncomfortably...I`m still going to go against the grain on this one...on my last 1/4 mile session..there is bumps halfway down the strip...in the power it kept going into slappers consistantly all day unless I short shifted or rolled off ...it`s my understanding that the front wheel is just kissing the tarmac & is unloaded hence free to skip left & right over bumps ...less power means more weight on the front...I`m sure most have had the bars go mental accelerating hard over a rough road & it`s been my experience that the osscilations gradually increase unless you roll off...
I`m not naive however & know that there are different reasons for each tankslapper of course as described in the above post where the front went spastic when the rider shut off during the aborted overtake mentioned...
What ever works for the rider.
From reading your post I think you're talking about rolling off prior to a bump to avoid a tank-slapper .... whilst the other people on this post are saying don't roll off [wind-on] one you're already in one.I`m not naive however & know that there are different reasons for each tankslapper of course as described in the above post where the front went spastic when the rider shut off during the aborted overtake mentioned...
What ever works for the rider.
Edited by FM on Monday 19th November 11:26
Some hard acceleration out of a bend and catching a bump at same time can have the desired effect!
Usually find it gets worse if you slacken off, so relax, grip tank with knees and pray. Steering dampers can help but only assist as "biker's nemesis" can testify to, as both he and I have had some pearlers
. A good tank slapper can have the result of feeling good when you save it or broken bones in hands & wrists along with enlarged purple gonads if unsuccesful!
Oh,a possible empty wallet too.
Usually find it gets worse if you slacken off, so relax, grip tank with knees and pray. Steering dampers can help but only assist as "biker's nemesis" can testify to, as both he and I have had some pearlers
. A good tank slapper can have the result of feeling good when you save it or broken bones in hands & wrists along with enlarged purple gonads if unsuccesful! Oh,a possible empty wallet too.I used to ride big bikes some 30 years ago, and experienced tank slappers then. The advice given in some of the foremost biking magazines was to either back off the throttle or open it up a bit more, the logic was that tank slappers occur at specific speeds and by either slowing or speeding up you should be able to come through it. I don't know if speeding up stopped them cos I always shut the throttle and that worked for me.
catso said:
I've had a few slappers over the years, luckily never crashed because of one but it is my understanding that easing off is the wrong thing to do, kind of like in a rear slide the right thing to do is the unnatural thing ie to power through it and above all remain calm & relaxed, don't tense up.
Steering damper should help control it, my 916, with damper, has never done anymore than a minor bar wiggle and even then only under worse-case conditions.
I had one of the first Blades... More slappy than a very slappy thing. I used to relax my grip, open the throttle gently and move my weight forward. Always worked for me over the years, luckily never crashed because of one but it is my understanding that easing off is the wrong thing to do, kind of like in a rear slide the right thing to do is the unnatural thing ie to power through it and above all remain calm & relaxed, don't tense up.Steering damper should help control it, my 916, with damper, has never done anymore than a minor bar wiggle and even then only under worse-case conditions.
Fighting it is usually the worst thing you can do, just let it shake it's head a bit and go with the flow
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