12GS Unstable in high speed

  • Thread starter Thread starter Milano33
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Milano33

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Hi guys. My GS ('08) has developed a certain instability in riding over 120km/h (cca 70mph).
It feels like "waving", or more like the bike leaning towards right and left constantly. I used to have similar feeling driving through turbulence behind a van or a lorry.
It has started when the bike had about 16,000km on the clock. I changed both tires thinking it could be the reason. It did not solve the problem and over time was getting worse even to lower speeds. During 20k km service (12k miles) my dealer replaced the front suspension under warranty, because they thought that was the case. After that the bike handles much better in lower speeds, but the "waving" in high speed is still there and makes me worried. BMW has no idea what it could be... Any similar experience? Any ideas? Many thanks.

More info: the bike has never crashed, 95% of time driven solo, no offraod, no adjustments to aerodynamics...
 
What weight are you and how much preload are you running on the rear shock?

My experience is that running almost maximum preload on the rear and the second notch on the front puts more weight over the front of the bike and increases both the straight line stability and the bike's rate of turn.

HTH
 
I am 100kg and I adjust the rear shock depending on the luggage I carry. Normally medium to hard.

But I tried all the various positions of the pre-load adjustment after the problem started... No luck - still there :(
 
No puncture seal.

By the way, both rims (spokes) and wheel balance re-checked and is OK.
The problem is still there when driving both light or fully loaded with panniers. M. :nenau
 
I would say either tyre pressures or incorrect suspension set up. as said more rear preload may help
 
Milano33 said:
Hi guys. My GS ('08) has developed a certain instability in riding over 120km/h (cca 70mph).
It feels like "waving", or more like the bike leaning towards right and left constantly. I used to have similar feeling driving through turbulence behind a van or a lorry.
It has started when the bike had about 16,000km on the clock. I changed both tires thinking it could be the reason. It did not solve the problem and over time was getting worse even to lower speeds. During 20k km service (12k miles) my dealer replaced the front suspension under warranty, because they thought that was the case. After that the bike handles much better in lower speeds, but the "waving" in high speed is still there and makes me worried. BMW has no idea what it could be... Any similar experience? Any ideas? Many thanks.

More info: the bike has never crashed, 95% of time driven solo, no offraod, no adjustments to aerodynamics...
Click to expand...

I had exactly the same issue on a '08 GSA - so much so that when it first happened I nearly crashed at high speed and had to do some unthinkable things to get the bike under control.

I had ultraseal in both tyres - riding solo with luggage (20kgs max). ESA was set to 2up with luggage . I weigh about 100kgs.

It only ever happened on this bike and I have had a number of GSA. I was convinced it was the tyres but nothing scientific to back up that assumption.

The experience caused me to sell the bike but the facination of the GSA has made me purchase a new one - so maybe it was a temporary scare.

karl
 
Are you running with luggage?

I rarely use a top box because it unsettles my GS-A at motorway + speeds and gets into a weave.
 
Put on center-stand and check for any movement or noise from the bevel drive bearings.
Check patzx strip down thread to see a knacked pinion bearing, IMHO that could cause the symptoms.
ALSO have you changed the tyres recently ? as I remember a thread on a dodgy [ I think they were recalled ] make and type of tyre on 12's causing just your problem as they wore and went out of shape.
 
Tourance exp by any chance

Mine went off at around 2k and was horrendous on the road tanks slappers etc
 
to Sgt Bilco: I dont have a TopCase, only side panniers. It does it with or without them.

to Proff: The whole drive checked many times by myself and also BMW, it is in line, no noises, no symptoms...

to HRH OONYACK: the problem developed when I had almost worn out factory fit Bridgestone Battlewings. I thought that was the cause and replaced them with Tourance (not EXP)

I must add one thing. Even when the bike stands, when moving the handlebars from one side to another, the bike fells a bit "wague", just like if the frame is from soft metal. It reminds me of behavior of old (lets say 60-70tees) bikes with softer frames than we are used to nowadays.

Thanks all for responses and suggestions!
 
digger06 said:
are the steering head bearings loose/tight/worn?
Click to expand...

It feels tight. I have not done a proper check, but BMW had the front reassembled when changing the front shock and also the front forks oil and forks sealing which were leaking.

I assume the guys in BMW would discover this when doing the above.
 
As above they are very susceptible to tyre wear/pressure condition +top boxes do cause a weave above 100mph:augie .very sensitive to Preload and rebound ,one set up properly /change tyres/pressue should be UNSTOPPABLE!!:augie
 
My money's on the top box - I get a weave above 90mph only when I have the top box on. In BMW's defence, they do advise a maximum speed of 80mph with the luggage boxes on, although a two-up sprint fully loaded with all three boxes and a tank bag down an autobahn at 110mph proved this to be cautious, although I wouldn't say it felt planted! Stability has improved dramatically since I put Avon Azaro/Storm road tyres on it, and tyre pressures should always be first check. I only have two clicks of preload on the front shock, as I find it lifts all too easily when "making progress".......
 
The rear shock preload or ride height is adjusted using the round turning handle, it does not adjust the damping though. There is a screw at the lower part of the rear shock, try turning this to hard.

How baggy is you riding gear, could be the air is catching it

Good luck
 
Have you tried adjusting the screen?

I have noticed that this has an effect dependent on its position - when my screen was in the fully upright position (better protection but more buffeting) then the bike was noticeably more unstable at motorway speeds. Ive now backed it off a few notches and it feels much better. Worth having a fiddle. You never know, even tho you may not have changed it, your dealership might have when they were working on the bike.

While you are at the front of the bike just check the Torx pinch bolts that hold the fork legs into the bottom yoke - these seem to have a habit of loosening off (its unlikely to be this but elimination is the name of the game)

And lastly, as you have spoke wheels, it worth checking the "run out" on them - should be within 3 mm I think - just stick the bike on its centre stand and rotate them for a quick visual. IIRC spoked wheels tend to "settle" over time and can cause all sorts of interesting handling issues dependent on how far they may have come out of spec.

Good luck
 
Check the bolts of the bridge holding the forks right above the front fender. If you say the hadlebars at standstill feel soft that might be it. These have a tendency to loosen up anyway
 
Milano33 said:
Hi guys. My GS ('08) has developed a certain instability in riding over 120km/h (cca 70mph).
It feels like "waving", or more like the bike leaning towards right and left constantly. I used to have similar feeling driving through turbulence behind a van or a lorry.
It has started when the bike had about 16,000km on the clock. I changed both tires thinking it could be the reason. It did not solve the problem and over time was getting worse even to lower speeds. During 20k km service (12k miles) my dealer replaced the front suspension under warranty, because they thought that was the case. After that the bike handles much better in lower speeds, but the "waving" in high speed is still there and makes me worried. BMW has no idea what it could be... Any similar experience? Any ideas? Many thanks.

More info: the bike has never crashed, 95% of time driven solo, no offraod, no adjustments to aerodynamics...
Click to expand...


Milano33,

I've just bought a new 2008 1200 GS and I know exactly what you are referring to as I get the same feeling. I put it down to my being a well built person and I have been told to gradually increase the rear shock pre-load testing it each time as this will eventually cure the problem.

john1215
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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