this may sound stupid but..

[conure]

whats a tank slap(per) is it when the bottom of the bike hits the ground?

[Rob]

Nope, it's when your handle bars start slapping from side to side - usually when you are accellerating hard and hit a bump.

Can be quite an err 'interesting' experience!

Some bikes are more prone to it than others e.g. an R6! (I'm sure Keith can explain more). If your bike is prone to slappers you can add a steering damper to absorb some of the initial force and reduce the effect.
____________________
Love is 1050cc

[mr.z]

The dreaded tank slapper is when the front wheel is turned a different direction than your bike is traveling usually from hitting something i think (but depending on the geometry of the bike it will be more/less likely), the gyroscopic forces will correct itself but this can be extremely violent, best thing is to let it sort itself out and let go of the bars :O the reason its called a tank slapper is the bars smack the tank side to side violently at full lock, keeping control at this point is nigh on impossible...

Thats it as i understand it i might be wrong...
Theres a video of somebody having a REAL one at the TT somebody will no doubt post anytime soon.
____________________
>RidingSkills<->Tech Tips<->MyBikes<

[Scouse]

I had one of my own last night, riding along on my way to shauns after a quick ride home when I hit a bump. That was when the ride got interesting and I thought I was going to be on my behind up the dual carriageway . Must say it's a very frightening thing to happen, don't think I spoke to anyone for about half an hour. Oh well I survived but I won't be in a hurry to do it again.

[ProXimaCore]

I had no idea what a tank slapper was either, but I wasn't brave enough to ask. Had one today for the first time then. Knee down round a big roundabout (yes!!! I can do it on the right side too now!) Hit a bump in the middle of it and the bike sat straight up and the bars were all over the place. Luckily, as it sat up I was going directly for my exit (while wobbling franticly). Whew. Didn't think too much of it and continued to blast down the road for the next knee down.
____________________
Honda NSR125R -> Suzuki GSXR400R GK76a -> Kawasaki ZX636 B1H -> Honda CBR400RR NC29 -> Nothing

[Kickstart]

Hi

A real tank slapper is when the bars go lock to lock repeatedly. They are VERY violent, and are quite likely to throw you off the bike (a friend broke his collar bone from one on a 350LC years ago). Few bikes are prone to them, and I would doubt anything modern will suffer from them unless there are other problems. The old RD250LC used to suffer from them. Basically it is when the bike shakes its bars to the lock stops, but just happens to do it at the natural resonent frequency and so keeps doing it.

Loads of bikes will shake their heads under acceleration. Quite a few will maybe go lock to lock hitting a bump under hard acceration. Virtually none will go into a full on tank slapper.

If a bike does go into a tank slapper while you are riding it, you will be quite lucky to stay on, and you will certainly not be in control of the bike while it is doing it.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[mr.z]

THIS is a tank slapper, you know when you have had one when you wake up in the hospital... Very scarey indeed...

Major wobbles are just as scarey though i'd imagine, like i said best thing is to let it sort itself, if you hold on all you do is transfer the wobble allover the bike and it will waggle its ass allover the place and take you with it!

Like said perviously its down the geometry of the bike and all it needs is quirky suspension and a bump and off you go! for example, you don't hear of many on cruisers.. Think if i had an R1 or similar i'd be having a steering dampener fitted sharpish just to be safe...
____________________
>RidingSkills<->Tech Tips<->MyBikes<

[izzi81]

that is a very very scary bit of video..

[John]

Yeah, scary video. Would not like to be riding that bike.

Looks like the rider was OK though? He didn't hit anything as far as I can see. It actually looks quite funny the way his head is moving about.

Lucky the curb was there too, or the man with the flag might have got hit by the bike. :/
____________________
TT600 neeeeeeeeeeeeeeeeeeowwww!

[T.C]

Tank slappers are not as common as they were say 10 years ago, but they do still happen from time to time, and mostly it is as a result of poor weight distribution or poor airflow over the bike.

There is a video produced by Dunlop called "Wobble and Weave" although it is a bit old now, where the causes of a tank slapper are explained in great detail.

The most common cause is where someone has been hooning along and then suddenly sits up into the air stream causing the flow of the air around the bike to become unsettled too quickly. This causes the front end to go light and the subsequent weight transference causes the front wheel to start oscillating very quickly. The way to cure it is to lean forward back onto the tank and then sit up gradually as you reduce your speed.

The other way is caused by poor weight distribution, particularly where panniers and top boxes are loaded down but it can also be caused by soft luggage. Because there is so much weight to the back of the bike, the front end is permanently light again causing the steering to move around, or by a particularly lightweight rider on a heavy bike.

The best example was the Suzuki TL1000S which lost sales because of reports of big slappers, but it only affected the bike when being ridden by lightweight riders, and all because of the reasons mentioned above.

If you can track a copy of Wobble and Weave down it is well worth a look.
____________________
It is better to arrive 30 seconds late in this world, than 30 years early in the next

[priller]

[Hex]

[True Blue]

here is a video of a tank slapper
____________________
Past >>>> Honda NSR 125 >>>> Suzuki GSXR 600 K1 >>>> Suzuki GSXR 600 K4 >>>>Kawasaki Z1000 DAF >>>>Suzuki RMZ 250 >>>> Current >>>> KTM Superduke R 1290 >>>>

[priller]

[G]

Following Dusty on his R6 I've seen one that /did/ look like he was going to throw him off. Did actually quite scare me at the time.

I believe the two common misconceptions with sorting out tank slappers are: a) Braking... generally you should try to power out of them, braking can make it worse.
b) Trying to hold the bars stiff... this just transfers the 'shake' to the rest of the bike.
Can't be bothered to think about/go into the theory at this time in the morning though .