O-rings that are worn won't create a good seal around the shock shaft
and could let fluid out of the shock, or worse-dirt in. The tool can at
least help you find out how the O-rings are holding up.
STEP 1. Remove the springs and fluid from the shocks. It's best
to also remove the piston, but the seals on some shocks may be damaged
if the shocks are fully extended with just the bottom E-clip on the shock
STEP 2. Install the shocks on the tool without the springs installed.
STEP 3. From a fully compressed position, extend the shocks almost
to full extension. The gauge indicator will point toward the shock with
the better O-rings. If the indicator points dramatically to one side,
you might want to replace the O-rings.