Tank slappers

[Big Bird]

Hi

I've had my 800 for a year and have taken it to Morocco and back, with not too many issues, but yesterday I had to ride about 300 boring motorway miles.

At around 85 to 90 I continually got a bad 'weave' on the bars. I discovered this was less pronounced if I moved my substantial arse back onto the pillion seat.

I have TKC's fitted and was riding with a single top box.

Anyone experience the same or know of a cure?

 

[Phluppe]

What you're feeling is known as "High speed weave", mostly caused by not having enough weight on the front ('cause that's where the motion starts).

You feel it at the back though, so most people never think of the front as the starting reason. A top box, causing a bad turbulence alone can be enough reason to start weaving. Next time try placing your weight to the front, and see if it stops weaving.
Also, TKC's are not the best high speed tyres around, might very well be one of the causes.

Be carefull though, if the weave is strong enough, your rear tyre might start going left and right oncontrolebaly, and finally slide from underneath you, not something you want to enjoy. In case it gets really bad, pull the clutch, that alone increases grip on the rear, which might avoid the tyre from sliding away.

Grtz, Philip!

 

[johnboy]

Hi

I've had my 800 for a year and have taken it to Morocco and back, with not too many issues, but yesterday I had to ride about 300 boring motorway miles.

At around 85 to 90 I continually got a bad 'weave' on the bars. I discovered this was less pronounced if I moved my substantial arse back onto the pillion seat.

I have TKC's fitted and was riding with a single top box.

Anyone experience the same or know of a cure?

I used to get the same problem which I have put down to the TKCs as with the opriginal road tyres there is now no weave. Probably therefore just the difference in tread pattern.

 

[Big Bird]

What you're feeling is known as "High speed weave", mostly caused by not having enough weight on the front ('cause that's where the motion starts).

You feel it at the back though, so most people never think of the front as the starting reason. A top box, causing a bad turbulence alone can be enough reason to start weaving. Next time try placing your weight to the front, and see if it stops weaving.
Also, TKC's are not the best high speed tyres around, might very well be one of the causes.

Be carefull though, if the weave is strong enough, your rear tyre might start going left and right oncontrolebaly, and finally slide from underneath you, not something you want to enjoy. In case it gets really bad, pull the clutch, that alone increases grip on the rear, which might avoid the tyre from sliding away.

Grtz, Philip!

Hi Philip

Thanks for this, but it seems like I'm getting the complete opposite of what you are saying. I only feel it at the front and it gets better if I move my weight further back.

 

[freeloader]

I was experiencing a weave on my F800GS, at about 65mph and above, with the following fitted:

BMW alloy panniers (no topbox)
Metal Mule screen
TKC tyres
Nippy Norman winglets.

Took the winglets off and got an immediate, though not complete, improvement.

Replaced the MM screen with a Calsci one, and got another, smaller, improvement.

May not be any use to you, but I don't know what screen, etc., you have fitted...

 

[v8legend]

Hi

I've had my 800 for a year and have taken it to Morocco and back, with not too many issues, but yesterday I had to ride about 300 boring motorway miles.

At around 85 to 90 I continually got a bad 'weave' on the bars. I discovered this was less pronounced if I moved my substantial arse back onto the pillion seat.

I have TKC's fitted and was riding with a single top box.

Anyone experience the same or know of a cure?

Sounds to me like your rear tyre is squaring off. TKC's aren't designed for directional stability, and they don't get any better when they wear out.

 

[elevensies]

tank slippers? blimey, i been using bike boots all these years

 

[Myke Rocks]

Just check this

No, I am not saying this is your problem, but check that the front wheel spindle is properly tightened & clamped. If not, a tank slapper becomes a probability.
Myke

 

[mechcanico lee]

My vstrom used to get a gentle weave around the same speed, if i sat further back it used to stop or if i rode it without the top box it was ok also.

I think that sitting further back just changed how the air flow comes over the top of you and the topbox, just some thoughts.

 

[Tim Cullis]

I got it a lot on my F650GS with TKCs fitted and found that sticking higher pressure in the front tyre helped considerably.

 

[Klanky]

Check the tyre pressures and try adjusting them up and down a couple of pounds - see if that makes any difference.

I run on TK's and tbh I've only ever noticed the steering getting a bit vague at 90-ish. But it's very rare I'm at those speeds for anything more than a short burst, so i just don't bother about it.

 

[RICHO]

tank slapper

My wife has a f650 twin and just been on a trip with top box and metal mule pannier,s on could,nt go over 80mph has it started tank slapping real bad , Just changed both tyres and it seems to have cured it But they were well flatted in the centre ...

 

[Big Bird]

Wow - a lot of possible causes, the tyres are new. I have a MM screen.

I'll try the tyre pressure thing, or maybe stay below 90 with a top box. Maybe the slippers will help!!