Don’t be afraid to experiment. When MXA is testing a
bike with harsh forks, we try all of the clicker variations.
We even slide the forks up in the triple clamps to transfer
more load to the front to help the forks break through the
crust. When push comes to shove, we pull the forks off
the bike and pump out 10cc of oil from each leg. On air
forks, we only lower the oil height on the damping leg,
not the air-pressure side. If the forks are still harsh, we
remove 10cc more. There are forks that we have removed
40cc of oil from in order to get them plush enough to
race with. The caveat here is that you can only lower the
oil height to the point where the forks start to bottom
on your local track. Once the forks bottom, you need to
add fork oil back in. Check your owner’s manual for the
maximum and minimum oil heights allowed for your bike.
Adjusting your oil height is a valid tuning process and,
best of all, it is free. It should be noted that if all else
fails, MXA has its favorite suspension shop’s phone
number on speed dial.
It’s no secret that the MXA wrecking crew does everything in its power not to send the forks on its test bikes out to get re-valved. It’s not that we
don’t believe that the suspension shops can improve the
performance of the forks; it’s just that we don’t want to
do it. We are stubborn. We are cheap. We think that we
can find a fork fix without having to resort to spending
hard-earned cash. We click the clickers in every imaginable way, and when that fails, we change the fork oil
height. Fork oil height is the magic that every suspension
tuner keeps hidden up his sleeve. It works. It is free.
And, it doesn’t require taking the forks apart.
What is the effect of changing oil height? Adding oil
to your forks reduces the air volume in the fork leg. Air
is compressible, and a smaller air space is harder to
compress than a larger air space, so reducing the air
volume results in a stiffer fork. Since the compression
of the air space is gradual, lessening the air space will
be felt by the rider from the middle of the fork’s stroke
to the point of bottoming. In essence, adding oil to your
forks makes them stiffer from the midpoint on.
The obvious corollary is that when you take oil out of
your forks, you make them softer from the mid-stroke on.
Adding or subtracting oil has a negligible effect on the
first 4 inches of travel.
How do you add oil? The simplest way to add oil to
a fork is with a graduated syringe that has a tip on it
small enough to fit in the air bleed screw on the fork
cap. Use the graduated scale to siphon 10cc of fork
oil into the syringe. Noleen sells an affordable syringe
for $6.95. Call them at (760) 955-8757 or go to www.
noleenj6.com. Insert the syringe tip into the air bleed
hole so that it has a good seal (if it doesn’t, oil will leak
out without going into the fork). We remove the O-ring
from the air bleed screw and put it back in the hole
to seal the syringe better. Slowly squirt the 10cc of oil
into the forks. It is important to note that as the 10cc of
oil goes in, 10cc of air must come out. Bleeding the air
while inserting the oil is tricky. The easiest way is to
push down on the syringe to squirt in about 1cc of oil,
then pull back on the syringe plunger to allow air bubbles to escape back into the syringe. This back-and-forth
motion is tedious, but it is easier than pulling the forks
apart. The whole procedure can be done with the forks
on the bike.
How do you lower the oil height? First, you have to
remove the forks from the bike. With the forks off the
bike, take the air bleed screw out of the fork cap. Turn
the forks upside down and place a graduated cup (the
syringe with the plunger removed works great) directly
under the air bleed-screw hole. Gently compress the
forks by hand to force oil out of the fork. Don’t worry
about it spraying out; it doesn’t want to come out. Once
the graduated cup says you have removed 10cc, stop
and do the other fork leg.
What can be achieved? Taking 10cc of oil out will
make the fork feel softer from the mid-stroke on. It is the
simplest and quickest way to take mid-stroke harshness
out of stock forks. If your forks are too stiff, don’t get
full travel at your track or are too harsh, lowering the oil
height will make them feel suppler. Conversely, adding
oil will make the forks feel stiffer. More oil works best
when a rider has a bottoming problem.
MAKING FORKS BETTER FOR FREE