Tank slapper

[Mittzy]

I have only had a moment at 200kph on a bend with a classic screen.
Serious Sphincter puckering then......

 

[mully95]

I put my money on the Avon tire!

I had the exact same problem...... took the new Avon off and installed a new Metz on the front and the problem was gone. Avon balanced out but still had a broke belt or something. Tire changer at a dealership I take my tires too said Avons getting a lot of complaints.

 

[Nat67]

When I was a young bloke sometimes when I had a girl pillion and a tee shirt to tee shirt contact took place under intentional heavy breaking I experienced a tank slapper with both hands on the bars

I used to know two girls who where called Rhonda and Glenda. They came to be known as Rhonda Rottenbox and Glenda Gluepot. I can't remember why.

Rhonda Rotten box and Glenda Glue pot . I can only imagine !

 

[Rocket Scientist]

When I was a young bloke sometimes when I had a girl pillion and a tee shirt to tee shirt contact took place under intentional heavy breaking I experienced a tank slapper with both hands on the bars

 

[1olbull]

Did you have a load on the rear?
Does moving your weight forward over the tank help?

 

[mr hunt]

I don't normally do this but I took both hands off the bars to adjust my helmet whilst doing 70kph & the handlebars started wobbling from side to side gradually getting more violent.
I tried it at a few different speeds & it only seems to do it below 75kph. It's fine at 100kph.

The bike is a 2015 Rocket X running a Bridgestone Exedra Max on the rear & Avon Cobra on the front.
I took it to the dealer & they checked tyre pressures, wheel balance, steering head bearings & couldn't find anything wrong.
They've booked it in again next week to have another look.

I did notice that the bike steers slightly to the left when I let go of the bars on a flat road surface.

Is there anything else I could get the dealer to check?

I have the same combo and the same wobble

 

[MikeDeY]

I had the same issue with my last Cobra front tire. I thought for sure I had some bearing starting to fail. But when I replaced the front tire, the wobble went away.

 

[stollydriver]

Have you added anything that can upset the geometry of a bike like windshield, bags,floorboards, added on stuff to the crashbars or even crashbars? if all else fails keep your hands on the handlebar.

That reminds me of my dad - "look dad - no hands" followed by " look dad - no teeth".

 

[cootertwo]

Tank slapper will make it very hard to poop for a few days!

 

[TriumPhil]

The 140 cubes reciprocating under the tank will account for the pull off centre

Yes, this is something that all shaft-driven bikes will exhibit to one degree or another, more technically known as counter-rotational force [centripetal force (I think) created by turning of the driveshaft].

cen·trip·e·tal force
(sĕn-trĭp′ĭ-tl)
The force that pulls an object moving in a circle toward the center of the circle and causes the object to follow a curving path. Earth's gravity acts as a centripetal force on the moon.
Did You Know? In one popular carnival ride, people stand with their backs against the wall of a cylindrical chamber. The chamber spins rapidly and then the floor drops out, but the riders remain pressed against the wall and don't fall down. Why? Most people would say that the reason people"stick" to the wall is because a centrifugal, or outward, force is pushing them against it. In actuality, there is no outward force, no matter how strongly the people on the ride may think they feel one. In fact, it's just the opposite: the riders are really subject to an inward, or centripetal, force. As the ride spins, it forces the riders to travel in a circle. Objects (including people) in motion tend to travel in a straight line at constant speed unless they're acted on by some external force. To make an object travel along a curved path, you have to keep forcing it toward the "inside" of the curve.The walls of the ride do just that, pushing the riders toward the center; the friction between the riders and the wall holds them up, so they seem to defy gravity.

This gyroscopic action is also known as "shaft effect" and "torque jacking"...