This may help...lifted from another site..
Preload
is the static tension in the spring. It affects suspension travel, seat height and speed of steering but not 'hardness' or 'softness' of the ride (unless you hit the top or bottom stop).
The following ASCII art represents your spring when it:
is uncompressed (e.g. on center stand with wheel off the ground)
has low preload
has high preload
- ---------------------- - ------------------ -
| | |
| | |
| Uncompressed | LOW | HIGH
| spring | preload - preload
| length |
| -
-
Adjustment
Front: Adjust collar on bottom of shock using hook wrench and extension from the toolkit.
There are 5 notches.
Highest notch is LOW;
Lowest notch is HIGH.
Standard setting: second highest notch
Suspension travel: 190mm (BMW claim)
Ideal preload: 1:3 i.e. 63mm of 190mm travel
Rear: Set with large black knob by exhaust marked HIGH, STD, LOW.
HIGHer is clockwise;
LOWer is counterclockwise
Standard setting: as marked STD
Suspension travel: 200mm (BMW claim)
Ideal preload: 1:3 i.e. 67mm of 200mm travel
Set-up:
Sit on the bike wearing all your riding gear e.g. jacket, helmet etc
Adjust preload front and back so about a third of your suspension travel is used up.
(Helps if you've got someone to measure or else use a plastic tie on the suspension to see how much the shock compresses).
Adjust preload front and rear for:
increased loads eg touring/pillion go HIGHer
bumpy roads and off-road go HIGHer
smooth roads go LOWer.
Turn the adjuster:
HIGHer to:
increase suspension travel
raise seat height
speed up steering.
LOWer to:
decrease suspension travel
lower seat height
slow down steering.
Fault finding:
Suspension tops out, bike steers too quickly ("tucks") - preload too LOW so go HIGHer
Not enough ground clearance, suspension bottoms out, bike turns too slowly - preload too HIGH so go LOWer
Rear rebound damping
resists spring extending. When the spring is compressed it goes to a minimum length then springs back (i.e. rebounds). Rebound damping stops your *wheel* from bouncing, not you. Affects traction and how the ride feels i.e. "hardness" or "softness".
Rebound damping is connected to compression damping and vice versa. This makes finding the correct settings difficult. If you make rebound damping HARDer, the ride becomes harder but also if you hit a big bump, you are less likely to bottom out (than if you had SOFTer setting) i.e. same effect as if you had increased compression damping.
Adjustment
The rear rebound damping adjuster is that little black screw on the exhaust side at the bottom of the shock. Adjust using the screwdriver and extension from the toolkit.
Clockwise is HARDer
Counterclockwise is SOFTer
Only the last few turns towards HARD seem to have any effect.
Standard setting: turn clockwise to fully HARD then undo HALF a turn
Set up:
Ensure tire pressure and tread depth are correct and preload is set.
Carefully work out original setting and write it down (for reference and so you can change it back if all else fails).
Find a bumpy road, the bumpier and the larger the range of bumps ie small to large, the better. (Riding fast around a bumpy corner is best.) A roadside observer can help as well.
Now ride up and down your bumpy road. Start with one extreme setting (say HARD) then the other (SOFT) so you feel the sort of effect rebound damping has.
Feel what the back end is doing - you want firm traction not skidding.
Depending on the feel you got, estimate what initial setting to try (eg half way between the two extremes or more HARD than SOFT).
Try many settings (quarter turn) then write them down with their results.
The ideal setting keeps the back wheel most consistently in contact with the road. (It is NOT the smoothest ride, that's underdamped).
Note
BMW shocks go off very quickly - they heat up then stop working until they cool down again. This means, they are different at the start of your bumpy ride to (say) 15 minutes into it. Give them time to cool otherwise you are wasting your time.
Adjust rebound damping for:
increased loads eg touring/pillion go HARDer
bumpy roads and off-road go HARDer
smooth roads go SOFTer
To check settings for luggage/pillion, load up and try your bumpy road again.
