R1150 RS rear spring preload question

[CodyS]

So as I learn more about this bike I was messing with adjusting the rear spring preload.  Right now it seems to be fully counterclockwise (soft) which is the correct setting for me (single rider no luggage).  I wanted to make sure it at least functions properly. The knob is extremely hard to turn clockwise by hand and doesn’t seem to move like i assumed it would.  Looks like its mounted to the bike and has a banjo fitting on the bottom, assuming there is or should be some type of fluid in the reservoir if i remove it and pull the banjo fitting off?  Thanks for the assistance.

[Michaelr11]

23 minutes ago, CodyS said:

Looks like its mounted to the bike and has a banjo fitting on the bottom, assuming there is or should be some type of fluid in the reservoir if i remove it and pull the banjo fitting off?

 

1100/1150 Rear Shock Preload Service

 

This video from MotoFrog shows how to remove and service the rear preload adjuster.  Even if working properly, I wouldn't ride it on the softest setting - unless you are really really light.  I use a container of "jack oil" to refill the reservoir.

 

 

 

[CodyS]

Ok thanks for the link..Not sure how many turns it should take but  i cranked it and cranked it clockwise and it never seemed to move so looks like its time to pull it and have a look. 
 

Edit to see if there’s any alternatives to jack oil?

[The Fabricator]

The pre-load adjuster is a hydraulic oil filled cylinder connected via a hose a hydraulic oil filled cylinder on the shock.  As the adjuster knob is turned clock wise on the 'Adjuster' knob, which is attached to a screw, it pushes on a piston, moving it down in the adjuster cylinder thereby pumping oil through the hose in to the shock mounted  cylinder, moving that piston out, thereby compressing the shock spring.

 

If the knob is turned and the spring compression is changing, AND THEN it stops changing with more knob turning it probably means the adjusting mechanism is reaching the end of its' designed range.

ATF oil is fine.  

It might help to lubricate the screw [the knob is mounted on] to ease turning.  

 

It is to be expected that the knob will rotate somewhat easily when turned counter-clock wise, as the oil pressure is pushing in that direction of screw rotation.

It is also to be expected that when turning the knob clockwise that greater resistance will be felt as the oil pressure is resisting the screw direction of rotation.

Stated another way, CC wise, the oil pressure helps; C wise it henders.

To make the C wise turning easier, put the MC on the center stand, thereby reducing the oil pressure somewhat because the MC weight adds to the pressure.

It is STILL expected that compressing the spring will be harder than releasing spring pressure.

 

As regards the 'Proper Spring Preload',  there is no RIGHT AMOUNT.  

It is recommended by suspension companies that the amount of spring compression with load [you, passenger, luggage, etc.] is 30% of wheel travel.  And 5% to 10% of wheel travel with only the weight of the motorcycle.

This is a starting point.  

What I always recommend is adjust the spring as soft as you want to avoid harsh feeling, then adjust the damping soft also.  If the chassis wallows or has an indistinct feeling, increase the damping until it feels stable.

And it has to do with the road condition you experience.

I ride my GS on back roads which can be quite rough, so I want suspension compliance to reduce fatigue.

Smoother roads might not indicate softer suspension settings.

I do change the  spring preload between solo and w/passenger.  Damping also.

When adjusting the damping, be bold.  Turn the screw fully one way then the other to determine how many rotations there is in total.  Try a 1/4 to 1/3 of total at a time, then refine to lesser amounts.

There is no CORRECT setting.

[CodyS]

Update on this, I think I misspoke… the adjuster is the fully down position which i believe would be the max preload.  No amount of turning either way seemed to change anything, i pulled the reservoir off and as I suspected as soon as I cracked the banjo fitting it spewed a little very black oil so it was def under pressure.  I buttoned it back up until i have a chance to determine my next move as i will be commuting on the bike to work this week.

 

I’m not sure whether to just let all the old nasty fluid drain out and see if I can figure out why the adjuster won’t screw up and down and hope I can get the piston pushed back up so I can refill with fresh fluid or what. 

[dirtrider]

19 hours ago, CodyS said:

Ok thanks for the link..Not sure how many turns it should take but  i cranked it and cranked it clockwise and it never seemed to move so looks like its time to pull it and have a look. 
 

Edit to see if there’s any alternatives to jack oil?

Morning  CodyS

 

You can use ATF or power steering fluid  if that is all you have & are in a bind but it isn't recommended.  Best to use proper hydraulic oil (especially if you don't completely drain the remaining old hydraulic oil as mixing ATF with hydraulic oil is not advised). 

 

Hydraulic jack oil is usually available at Autozone, O'Reilly's, or even Harbor Freight. 

[CodyS]

1 hour ago, dirtrider said:

Morning  CodyS

 

You can use ATF or power steering fluid  if that is all you have & are in a bind but it isn't recommended.  Best to use proper hydraulic oil (especially if you don't completely drain the remaining old hydraulic oil as mixing ATF with hydraulic oil is not advised). 

 

Hydraulic jack oil is usually available at Autozone, O'Reilly's, or even Harbor Freight. 

Ok great thanks for the info, I will pick some up today.

[CodyS]

Update on this, got a recommendation on one of the BMW facebook groups to remove the screw that holds the adjustment knob on and turn the piston with a wrench, gave it about a quarter turn and it broke free and was moving as intended.  Removed the whole assembly and dumped the oil, pushed the piston back to the top and refilled with fresh jack oil, also used a syringe to draw some oil and fill the line through the small hole in the banjo fitting to top it off (it took about 1 cc to top off the hose before it started running back out).  Reinstalled everything seems to work fine now.  Aware that the shock is 18 years old but wasnt quite ready for a roughly $1,000 expenditure like that.  Just wanted to finalize the post in case anyone in the future runs across this issue.