Advice needed - oscillating handlebars

[gbreffitt]

Hi, I'm hoping someone here can give me some advice as to the problem i'm suffering with my GS 800?
Above 70mph, i'm getting alot of oscillating on the handlebars. They are moving back and forth about an inch.
Quite un-nerving at these speeds as you feel your fighting it.
Up to yet, I have had the wheel checked to see if it was buckeled, result was, no damage, no side movement, not buckled and spokes were all ok to within 15 thou. This was checked by a professional wheel builder/truer. I also had the wheel re balanced to see if that cured it and checked that the tyre pressures were ok as per the handbook.
So, could it be the state of the roads or the tyres or what?
I bought and had fitted a pair of TKC's in November 08, I have only done a few runs out over winter, road and off road use, no great mileage involved, only about 300 miles.
When they were first fitted, i tried them out to well above legal limits and was extremely impressed as they felt as smooth as the original road tyres.
I suppose the next thing to do is swop back to the battlewings to see if it's the tyre or something else.

Anyone else suffered this or have any ideas?

Thanks

 

[rob mac]

I had the same on my Blackbird, from new! After much fecking about at the dealers, including wheel balancing,head bearing torques etc the front tyre was found to be at fault with an internal defect that caused the problem. New tyre under warranty never a problem again. See if you can swap a front wheel with someone for a quick road test.

 

[gbreffitt]

Thanks Rob, I bought the tyres over the net, not sure where I would stand with warranty?

 

[everywherevirtually]

mine now oscillate above 70mph since fitting the TKC 80's. I can't describe them as being as smooth as the Battlewings as they clearly can't be. The TKC's are not designed to blast down the motorway above 70 mph. It's more akin to riding on 50p's but I expected that and I actually quite enjoy it.

I have images of the Dakar riders blasting across the pistes as their bikes squirm through the dirt.

If you have checked everything else over I wouldn't worry about it. Its the nature of the beast that is a knobbly tire.

 

[Ozkiwi]

Have you just pur hand guards on by any chance.
The wind buffeting will cause this type sensation

 

[chrisjk]

It's the TKCs - don't worry about it. The movement doesn't really get any worse and you'll find you can cruise at 80 comfortably enough once you get used to it. The bike is still perfectly controllable.

 

[gbreffitt]

Have you just pur hand guards on by any chance.
The wind buffeting will cause this type sensation

No, I had 1200 gs hand guards on from new but switched to barkbusters.

 

[gbreffitt]

It's the TKCs - don't worry about it. The movement doesn't really get any worse and you'll find you can cruise at 80 comfortably enough once you get used to it. The bike is still perfectly controllable.

So is this common to the tyres?

I used mitas enduro tyres on my old ktm 525 and never experienced this motion

 

[RickG]

I've no experience of TKC or even a GS800 but it's something older gits like me used to experience back in the 70's when bikes and tyres were somewhat less advanced. Disappearing though a hedge whilst undergoing a wild tank slapper on an early two-stroke triple wasn't unheard of. Part of it is due to the castor effect of the steering, it's what keeps the steering self-centering but there is a natural frequency of oscillation that is speed dependent. Normally the designers can ensure the oscillation is outside normal road speeds. However, certain things can begin to induce a wobble as the bike reaches a characteristic speed where the tendancy to oscillate is greater:


low tyre pressure, esp' rear.
worn swinging arm bearings
tight head races
too much wieght too far back (I found carrying a 50kg bag of cement on the back of my 650 Triumph often made it start to wobble...)
a general mis-match between the tyre and the geometry of a particular bike - some bikes just hated some tyres. Note that the rear tyre can be to blame, not the front.

However, given it's not an unheard of phenomenon I reckon you will have to live with it or swap the tyres back to something better suited to tarmac

When it start to wobble, try leaning forward for a moment or two. I used to find that would stop it as the wieght distribution and geometry of the bike alter slightly.

 

[lawe]

mine now oscillate above 70mph since fitting the TKC 80's.

What air pressure do you have in front? TKC with low pressure can be a bit wobbly on the highway.

/Lars

 

[gbreffitt]

What air pressure do you have in front? TKC with low pressure can be a bit wobbly on the highway.

/Lars

32psi

 

[lawe]

32psi

That's what I also have, so that can't be the problem

 

[gbreffitt]

I've no experience of TKC or even a GS800 but it's something older gits like me used to experience back in the 70's when bikes and tyres were somewhat less advanced. Disappearing though a hedge whilst undergoing a wild tank slapper on an early two-stroke triple wasn't unheard of. Part of it is due to the castor effect of the steering, it's what keeps the steering self-centering but there is a natural frequency of oscillation that is speed dependent. Normally the designers can ensure the oscillation is outside normal road speeds. However, certain things can begin to induce a wobble as the bike reaches a characteristic speed where the tendancy to oscillate is greater:


low tyre pressure, esp' rear.
worn swinging arm bearings
tight head races
too much wieght too far back (I found carrying a 50kg bag of cement on the back of my 650 Triumph often made it start to wobble...)
a general mis-match between the tyre and the geometry of a particular bike - some bikes just hated some tyres. Note that the rear tyre can be to blame, not the front.

However, given it's not an unheard of phenomenon I reckon you will have to live with it or swap the tyres back to something better suited to tarmac

When it start to wobble, try leaning forward for a moment or two. I used to find that would stop it as the wieght distribution and geometry of the bike alter slightly.

Went out today and didn't notice the wobble anywhere near as bad. Could be partly down to high cross winds yesterday. Thanks for the reply, I hadn't thought that it could be caused by the rear wheel. I'll check tomorrow.

I did find that i lost the wobble whilst the front wheel was cruising 4 feet above tarmac though! (for about 10 foot)

 

[everywherevirtually]

I haven't been down to the bike tocheck the pressure today but it was never an issue for me.

Tyre pressures change with the weather. Today it was 14c in Manchester. A few weeks ago it was in the minuses so that will have an impact.

Like I say a slight rumble from the knobbly tires doesn't bother me. I'm keeping the speed down below 70mph anyway because I want to prolong the life of the TKC's.

 

[mystic]

IMO this is all tending towards a bit of anal introspection ................................. just Ride & Enjoy!

 

[gbreffitt]

IMO this is all tending towards a bit of anal introspection ................................. just Ride & Enjoy!

Thanks for your input and taking the time to give me your opinion. It wasn't quite as helpful as the other replies. I would have thought if someone finds this thread a bit anal, why would they take the time to tell me? Unless of course, you are a bit Anal and feel the need to comment on everything?

Cheers

Quite correct on the introspection bit though, after all, thats why I posted it up!!!!! If it wasn't, I wouldn't have!

 

[everywherevirtually]

IMO this is all tending towards a bit of anal introspection ................................. just Ride & Enjoy!

+1

I agree. I don't worry about stuff unless it's falling off. Thats why I ride a bike and gave up my car.

 

[philipwal]

Had similar problem, but either with battle wings and metzler karoo, found out it was the torque on the neck, steering was too light and caused wobble at lower speed on gravel and higher speed on tarmac, now all fine again, check that neck bearing!

 

[Joe Bar]

IMO this is all tending towards a bit of anal introspection ................................. just Ride & Enjoy!

+1

I agree. I don't worry about stuff unless it's falling off. Thats why I ride a bike and gave up my car.

What's anal about wanting your bike to perform as it should, and when you clearly know it's not, asking for some advice and input from the collective. Even more so when you don't know the guy or his riding experience / ability from Adam

I had a similar weave issue with my Megamoto, when coming off bumpy, quick corners, which spoilt the bike for me. Asking here and on AdvRider, plus KTech got me some pointers towards the right direction, and after a lot of trial and error I managed to dial almost all the weave from the bars via the suspension settings.

I was almost at the point of ordering £500 worth of steering damper kit from the States to try and dampen it out, but that would just have masked what was really happening. Now the bike is great and rides a treat, and I do just ride and enjoy.

........ just Ride & Enjoy!

........ is what we all want to do surely, but if the bike's not performing as it should, then you're just not going to get the best out of it. By all means ride yours 'til the bits drop off, but some of us are looking for a little bit more from our bikes, thanks.