Wreck this morning - need ideas on cause for loss of control

[twinwillows]

So I'm minding my own business riding into work this morning & enjoying the cool air. Rounding a gradual left turn leaning a little as I do when out of no where the bike starts a real soft shimmy/shake. As I let off the gas & start to straighten up the soft shake goes into a fast violent shake back & forth making me loose control & going off the high side of the curve & over into the grassy ditch. Somewhere in all of this I get off tumbling & rolling. Judging from the trashed windshield & backrest & handlebars the bike must have flipped.

Wearing full leathers, gloves, boots & helmet but got some bad road rash on left forearm where sleeve slid up while I was sliding on my arm. Other than that I'm just sore from tumbling.

Neighbor helped me & my wife get the bike onto a trailer.

Question: Does any one have an idea what the shake could have been caused by? I have a new front tire on the bike w/less than 500 miles so I'm thinking it's more likely a front wheel bearing..

Thanks
Twin

[DGXSER]

First of all, VERY glad to hear your not hurt any worse!!!

Could be anything from loose lock nut on the triple trees to you hit a slick spot in the road that just got the front wheel going. Very hard to tell and if the bike took that big of a hit, it may not tell you either, as the damage may hide the cause.

[Ken Talbot]

Lack of air pressure?

[3Phase]

Willows, glad you're okay! It could be loose/bad bearings in the steering head or the swingarm.

[b.walker5]

I'm with Ken on the air pressure theory, although I'm thinking more like puncture or sudden loss of pressure. I've had front end wobbles from wheel and steering head bearings before and in my experience throttling off, and straightening up usually corrects, or at least lessens them. To get a tank slapper, big enough to spit you off, going I tend to think tyres. May not be the front one though. Check both tyres for air/correct pressure.

Glad you're okay. From personal experience i know the road hurts...

[petejw]

glad your ok,
and didnt get hurt to much.

with out starting arguements about riding skills,
u should never back off the throttle when a front
wheel shimmy starts, it will cause the shimmy to get worse, causing the rear end to swing around to the front, and toss you over the handle bars.
if possible slightly accelerate or keep the throttle even and ride
the shimmy out. easier said than done i know.

[b.walker5]

Sorry Pete, dont wish to argue either, but I dont agree...

[petejw]

its all good brian.

[CatatonicBug]

glad your ok,
and didnt get hurt to much.

with out starting arguements about riding skills,
u should never back off the throttle when a front
wheel shimmy starts, it will cause the shimmy to get worse, causing the rear end to swing around to the front, and toss you over the handle bars.
if possible slightly accelerate or keep the throttle even and ride
the shimmy out. easier said than done i know.

I've heard the same thing somewhere before, regarding how to avoid tank slappers. Something about, "whatever you were doing when it started, do it just a little more until it stops". If you were accellerating, accellerate a bit more, if you were braking, brake a bit more. Of course, I have no experience to back this theory up, but that is what I remember reading somewhere once...

Glad you came out of the crash all in one piece though, Twin!

JAT, but could a fork brace have helped this one?

[b.walker5]

JAT, but could a fork brace have helped this one?

Quite possibly, especially if he has a special.

[Rickrod3]

Just some info

http://www.msgroup.org/tip.aspx?num=190

Check out the movie. Twin is this what happened to you?

http://www.triumphrat.net/riding-and...explained.html
Here is good explaination


rick

[Crusty Snippets]

Tank slapper

Interesting replies.
My first thought: It is these bikes, in stock trim they do not handle very well.
The front wheel flexes between the forks, the forks are soft so the front wheel travel is great. Around a corner the flexing may start the problem, or with the front wheel going up and down coupled with the angle of the forks, the length of the bike is changing which in turn changes the turning radius, which promotes wobbles.

The two answers above ( previous post ) do not address your problem IMO, you did not have the front wheel in the air, you just got the wobbles.

Riding in a straight line in sand can do this. The back wheel sliding out a bit can start this. The front suspension as I said above can start this.
Going straight ahead and reducing speed ( if possible ) while dampening the wobbles with your arms is about all you can do.

My experience with this:
Had a tank slapper on the Featherbed framed 750cc, 85hp Norton at the Seattle track doing about 80mph. My conclusion after so many years was that the rear tyre broke free. I have been through that same corner many times at the same speed. Only happened once, never again, no problem with air pressure or the bike. Was season high point champion open GP that year.

On the SV1000S Suzuki a few weeks ago doing 176 kph, eased a little for a gradual lefty then a righty entering the Malahat from the North. Moderate lean angle for the righty and the bike drifted wide on the corner. Needed to reduce speed and apply more lean angle to avoid hitting traffic going other way. The culprit: zero air in the back tyre, looked like it had been shot with a 22. Low air pressure will make the bike feel mushy. You need air in the tyres to give the traction required to set off a tank slapper. This is not the problem incurred by the guys that ride the Isle of Man TT when the front wheel gets airborne.

A well set up bike with a good stiff frame and good suspension does not need a steering dampener IMO.

MY SV1000S does have one, my SV650S does not have one. The 650 is better on the tight twisty roads.

Also check the steering head to be sure it is not binding or too loose.
Mine ( XS11 ) was binding.

Pleased you are okay.

Uncle Crusty, licensed to thrill since 1961.

[b.walker5]

Interesting replies.
You need air in the tyres to give the traction required to set off a tank slapper.

Each to his own experiences i suppose, but from my own experience, once again, Sorry i disagree.

Pretty much anything that upsets the stability of the front wheel can start a gyroscopic wobble that can very quickly turn into a tank slapper. I've had a few wobbles in the 40 odd years i've been on two wheels, and most have the have been caused by spongy tyres.

[Crusty Snippets]

Pretty much anything that upsets the stability of the front wheel can start a gyroscopic wobble that can very quickly turn into a tank slapper. I've had a few wobbles in the 40 odd years i've been on two wheels, and most have the have been caused by spongy tyres.[/QUOTE]

I can agree in part that a soft front tyre can help start the wobbles.
Would be similar to riding in sand.
I have had bikes wobble and bend under me and not go where I aimed them, but only one tank slapper.
69 500 Kawasaki and 71 Norton Commando. Another bad handling bike was the 650 Yamaha of about the same vintage.
The original poster has not told us if the tyre pressure was low.
With the wobbles we can just keep going, if the speed was not too great, or slow down a bit. A tank slapper requires more immediate attention.
My XS11 is currently doing minor wobbles often. Soon to be fixed.

Crusty

[ichiro360]

glad yur ok, but it seems like yur triple tree is loose