The stock compression and rebound
settings on every 2017 KTM are set
at 12 clicks out. For the average
KTM owner, whom we describe as a
“40-year-old rich guy,” the ballpark setting was 140 psi, 20 clicks out on compression and 12 clicks out on rebound.
Faster riders ran more compression,
and slower riders went farther out
than 20 clicks.
All was not rosy. We did have
complaints. The air-bleed screws use
a #20mm Torx wrench. Forget about
this on the air side; instead, just use a
10mm T-handle, because you will strip
the Torx out of the aluminum bolt. On
the damping side, the bolt is steel, but
we replace it with the Phillips head
screw from the old-model WP forks.
Slower or lighter riders might have to
lower the oil height in the damping
leg by 10mm or more to get full travel.
Additionally, the AER’s air pressure
rises when the forks build up heat and
as the sun gets hotter late in the day.
It’s a good idea to check fork pressure
at regular intervals.
KTM’s recommended air pressure
is listed on the fork sticker and in
the owner’s manual in bar, not psi.
No problem. The pump that comes
with your KTM has a switch to
change the digital readout from bar
to psi. Americans do not use bar,
which, as you remember from your
science classes, is 14. 5 psi). But, don’t
sweat the bar-to-pounds-per-square-inch equation—just use the switch on
the pump to choose everything short
of pascals. ;
COMMON-SENSE SETUP TIPS FOR WP AER FORKS
WP’s take on air forks is so unique that its forks share very little with other air
forks on the market. These forks are
ingenious in their simplicity. The WP
AER fork works on the same recy-cled-gas principles as a rifle. The AER
fork uses the compressed air that is
generated from fork movement to
dampen the fork on its return stroke.
And, it does this with no added moving parts. When the 34mm sealed-car-tridge rod’s piston goes by a two-way bypass, the air pressure in the
upstroke becomes the air pressure in
the downstroke. Thus, in one up-and-down movement, WP is able to use
the same air pressure in two different
directions. The damping is in the right
fork leg and consists of 36 adjustable
clicks of compression (on the fork cap)
and 36 rebound clicks (under the fork
leg). You can race these forks right off
the showroom floor.
It’s important to note that any recommended air-fork setting is totally
dependent on the weight and speed
of the rider. As a rule of thumb, MXA
doesn’t choose its settings for Pro
riders. The Pros favor jackhammer
settings that can’t be used by the
vast majority of motorcycle riders.
The trick to getting the most from
your AER air forks is to find the proper air pressure for your weight, speed
and track. In the case of all the 2017
KTMs and Husqvarnas, we think that
the recommended stock air pressures
are on the high side of the scale and
that most riders should work down
from there. How far down? We’ve
gone as low as 130 pounds, but we
typically start testing at the OEM-recommended air pressure and then
lower it in 2-psi increments until the
forks don’t feel like they are dropping
into their stroke. Typically, AER forks
ride high in their stroke with the
How did we arrive at the correct
psi setting? We put a zip-tie on the
right fork leg and then did two fast
laps. Back in the pits, we eyeballed
the zip-tie and lowered the air pressure by 2 psi. We kept doing this until
the zip-tie was within 1-1/2 inches
of bottoming. That 1-1/2 inches of
unused travel is the safety margin for
flat landings. Most MXA test riders
ended up in the 140- to 148-psi range.
Once we found the correct air pressure, we focused on the compression
clicker to get the feel we wanted.
STOCK AIR PRESSURES
KTM 125SX .............................. 123 psi
KTM 150SX .............................. 123 psi
KTM 250SX .............................. 147 psi
KTM 250SXF............................ 154 psi
KTM 350SXF............................ 154 psi
KTM 450SXF............................ 156 psi