101 on how to dial in, you really should measure the sag for starters.
I'm an Ohlin fan but to each his own. Considering a YSS on the GS after the Holiday's.
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The first thing to do after you install your new shock is to set the ride height. This is
accomplished by adjusting the preload on the spring. You will need a helper to take measurements
while you do this.
First, with the bike on the center stand, measure the distance from the rear axle to some fixed
point on the frame. Next sit on the bike and while balancing as well as you can have your
assistant measure again from the axle to the same fixed point on the frame. Subtract the first
measurement from the second one. If the difference, called sag, is more than about 1.5" dial in
more spring preload until your sag measurement is between 1.25 and 1.5 inches.
Once you have the preload correctly adjusted, start riding the bike to get an idea where to go
with the damping adjustments. These adjustments are much more subjective than the preload and you
will have to ride the bike under a variety of conditions to get an all around idea of which way
to go.
Compression damping controls how quickly the shock can be compressed when the wheel encounters a
bump. Note the bike's behavior on sharp-edged bumps such as broken pavement and patched pot
holes. If it seems to bottom too easily, add more compression damping. Go back over the same
piece of road so that you can compare. If the rear end feels too harsh and you get the sense
that the suspension isn't moving very much, try backing off the compression damping.
My personal preference is to use as little compression damping as possible while still preventing
excessive bottoming. Rebound damping controls how fast the shock can extend after being
compressed. Again observe the bike's behavior under a variety of road surfaces, throw in a few
twisty roads as well. Try to sense the behavior of the rear end after traversing rolling bumps as
opposed to the sharp edged ones described above.
What you are looking for is rises and dips that create a large amount of suspension travel. Try
to determine if the rear end settles quickly or does it bounce a couple times? If you sense any
"floating" or "bouncyness" increase the rebound damping. This may come across as a wallow or
weave in fast cornering.
If you dial in too much rebound damping the shock may not be able to extend from one bump in time
to handle the next one. In the case of several closely spaced bumps the rear end can actually
pump down. Check this by running over a railroad track (or some other series of closely spaced
bumps) a few times at different speeds. I have a perfect spot not far from my house where there
are two tracks in parallel.
If after traversing a series of closely spaced bumps you have a sense that the rear gets lower
after each bump or if the last bump in the series feels much harsher than the first you may have
too much rebound dialed in. Back it off and try again. You won't be able to set it up all in one
day, more likely you will gradually dial it in over a period of several weeks. It's strictly a
trial and error process but when you get it dialed to your satisfaction, you'll know it.
Keep notes so that you don't end up going in circles and remember as a general rule, if you
increase your spring preload, such as when loading the bike up or carrying a passenger (remember
you should try to maintain that 1.25 -1.5" sag between unloaded and fully loaded) you should also
increase the rebound to control the additional preload.
