F800GS unstable at higher speeds

[Baiazid]

Tested with extra weight on the back: my wife (56Kg).

I could go 120kmph with no trouble this time! Must be suspension + tires combo

[runnin4melife]

F800GS unstable at higher speeds... cannot figure out the problem... increase life insurance on wife, then put her on the back to test it out

[F800ekelley]

How did it ride 2 up on the gs never done that before yet? So has anyone dialed in the suspension what are. u setting the rear at

[F800ekelley]

Sorry what settings are you taking on the stock rear shock

[Steveman]

Originally Posted by Baiazid

Tested with extra weight on the back: my wife (56Kg).

I could go 120kmph with no trouble this time! Must be suspension + tires combo

Mhh..... that means more dynamic sag on the rear creates less wobbles. Are u using original rear shock/spring or did u change it?

Regards Steve

[Baiazid]

Originally Posted by Steveman

Mhh..... that means more dynamic sag on the rear creates less wobbles. Are u using original rear shock/spring or did u change it?

Regards Steve

Hi,

all is original

[Baiazid]

Originally Posted by F800ekelley

Sorry what settings are you taking on the stock rear shock

I am a n00b in suspension settings. Only worked on big knob to preload when I add extra weight

[TFB43]

If your triple clamps are not torqued it can cause the bike to be unstable. I had this issue and after the bolts were torqued down it went away.

[runnin4melife]

If the triple clamps are loose, yeah the bike is unstable... are you talking about your steering head? handlebar mount or where your triple clamps hold your forks. Many bolts on these, all of which are integral.

[Steveman]

Originally Posted by Baiazid

Hi,

all is original

Mh... I am baffled. I am sure it comes from the rear but dunno why......

[Snowy]

There have been a few postings that deal with this issue. ITSATDM found that lowering the front end cured it. As did I.

After a complete front end change, to a front that is about 40mm taller, I found that having more, or less ride height in the front seems to stop the instability. The standard ride height in the front seems to be particularly susceptible to ride height changes in the rear.

That's why putting your wife on the back fixed it. It's effectively made the steering angle much lazier than standard. Make the steering angle a bit quicker than standard by dropping the front end and you'll fix it too.


For 2 up fully loaded travel I went to a Ohlins rear, revalved and resprung with a 23kg/mm spring - the heaviest they make.

Solo I have no preload on it and I get about 60mm rider sag. With full preload and wife and gear I get 60mm. No instability.

[vtbob]

Lots of advice here...some good but pretty far out

If the bike was ok before you put the K60s on....it is HIGHLY probable that it is the tires or the mounting process.

Let's face it semi knobby tires are NOT designed for high speed...as best they are just OK. If you have checked the balance, check to see if the wheel is true(side to side and around) when it rotates, is the tire true when it rotates. do you have proper tire pressure.
PS also check your rear wheel and tire for true as well. tire inflation pressure.

If these are all ok....then have fun exploring some more of the far out recommendations here

[machinebuilder]

Originally Posted by Baiazid

I am a n00b in suspension settings. Only worked on big knob to preload when I add extra weight

How did you decide where to put it?

This setting (setting rider sag) does affect the steering geometry.

Think of the bike pivoting on the front wheel, if you raise or lower the rear of the bike (by adjusting your preload) you are changing the angle of the forks. If you get things at a bad spot it will be unstable.

The owners manual has a procedure for setting your preload.

I found this out when I rode a KLR, they are severely undersprung for a 200lb person + camping gear. The headshake scared the crap out of me.

[Snowy]

Originally Posted by vtbob

Lots of advice here...some good but pretty far out

If the bike was ok before you put the K60s on....it is HIGHLY probable that it is the tires or the mounting process.

Let's face it semi knobby tires are NOT designed for high speed...as best they are just OK. If you have checked the balance, check to see if the wheel is true(side to side and around) when it rotates, is the tire true when it rotates. do you have proper tire pressure.
PS also check your rear wheel and tire for true as well. tire inflation pressure.

If these are all ok....then have fun exploring some more of the far out recommendations here

Having used them, I'd say.....yeah...no.

Likely the tyres have exacerbated a problem that was already there but not so noticeable.

Tyre profile also plays a part here. In combination with rake and trail the wrong profile can make things go to shit very quickly.

I just fitted a Pirelli Rallye front....it's shit on road. I mean, it works ok, but the profile is all wrong. Handles so much worse than it has with just about every other brand of tyre you can buy.

Some of this is the tyre type, some the tyre profile, and some is a combination of the rake/trail and the weight bias.

It understeers like a mutherfucker. On tar, on dirt. Very disconcerting. Once you get used to it, very predictable. But it's hard to get used to skating the front end through a gravel corner at 100kph with wifey on the back. But you can do it.

[Baiazid]

Originally Posted by vtbob

Lots of advice here...some good but pretty far out

If the bike was ok before you put the K60s on....it is HIGHLY probable that it is the tires or the mounting process.

Let's face it semi knobby tires are NOT designed for high speed...as best they are just OK. If you have checked the balance, check to see if the wheel is true(side to side and around) when it rotates, is the tire true when it rotates. do you have proper tire pressure.
PS also check your rear wheel and tire for true as well. tire inflation pressure.

If these are all ok....then have fun exploring some more of the far out recommendations here

Yes, before these tires all was perfect.

Cannot say it does bother me too much since I don't travel often with 120kmph. Usually I do 100kmph. But it is the idea that is something wrong ....