R90/6 Shaking Its Head

[Owen Snell]

I'm getting a degree of steering instability on my R90/6 when crossing white lines at a shallow angle of attack. It seems to be getting worse as the rear tyre squares off a bit, although after 1,000 miles it's not that square yet. Is this something that just happens as the tyre wears, or does it indicate something else is amiss? It feels like it is coming from the rear end, but I can't find any play in the swing arm or wheel bearings.

 

[Rob Farmer]

Sounds like wheel bearings. They are taper roller bearings and need to be shimmed correctly to work properly. Of course nobody ever does and then wonders why their airhead tries to fling them off when crossing white lines or ridges in the road

Heres the official way to do it

A bit of light reading for you http://w6rec.com/duane/bmw/wheel_bearing/

 

[Schtum]

Which tyres are fitted? Back in the day, the only recommended fitments were Metzler and Continental. Anything else didn't have the sidewall stiffness to damp out the oscillations of the gummikuh frame. I certainly had one serious tank slapper on a friend's bike that was fitted with TT100s and a friend's brother was killed when his airhead went off the road and through a dry stane dyke. I confess to not knowing what people fit and what's available for these bikes nowadays but it's worth considering....

 

[Beemerboff]

The swinging arm and steering head bearings might need adjusting too, you might just have a combination of three slack bearings----.

 

[Owen Snell]

.......A bit of light reading for you http://w6rec.com/duane/bmw/wheel_bearing/

Thanks for the link.

 

[Owen Snell]

Which tyres are fitted? Back in the day, the only recommended fitments were Metzler and Continental.

Correct Continental tyres, about 1,000 miles on them. It's only since the tyre started to get bit of wear that the instability became noticable.

 

[chasbmw]

Correct Continental tyres, about 1,000 miles on them. It's only since the tyre started to get bit of wear that the instability became noticable.

I used to find that Metzlers used to do that.....

I think that modern tyres are a real improvement over what was fitted 40 years ago, even if the current contis are made with modern rubber mixes.

Currently I really like the Michelin Pilot tyres, made in the correct 3.25 and 4.00 sizes and they seem to combine agility with stability and really good levels of grip wet or dry.

This assuming that wheel, headstock and swinging arm bearings are all in good nick and set up properly.

 

[Kenny]

The tyre do actually go off quite quick...especially as you've discovered over raised hazard/lane markings etc...wait until it rains when your going over them

 

[chasbmw]

I used to find that Metzlers used to do that.....

I think that modern tyres are a real improvement over what was fitted 40 years ago, even if the current contis are made with modern rubber mixes.

Currently I really like the Michelin Pilot tyres, made in the correct 3.25 and 4.00 sizes and they seem to combine agility with stability and really good levels of grip wet or dry.

This assuming that wheel, headstock and swinging arm bearings are all in good nick and set up properly.

And the Michelins are still stabil after around 5000 miles

 

[Owen Snell]

I used to find that Metzlers used to do that.....

I think that modern tyres are a real improvement over what was fitted 40 years ago, even if the current contis are made with modern rubber mixes.

Currently I really like the Michelin Pilot tyres, made in the correct 3.25 and 4.00 sizes and they seem to combine agility with stability and really good levels of grip wet or dry.

This assuming that wheel, headstock and swinging arm bearings are all in good nick and set up properly.

It was not noticeable earlier this year and has got progressively worse, but I suppose the tyres probably just highlight other defects. Plenty to be looking at this winter.

 

[Owen Snell]

..........A bit of light reading for you http://w6rec.com/duane/bmw/wheel_bearing/

Done the 'shake test' front and rear and both of the bearings are set up tight rather than loose - the nuts only need to be snug for the play to be removed, less than 10 Nm to loosen once the play is removed. I'm guessing that tight rather than loose isn't going to affect the handling?