(1) The difference. Apart from the glitz and
glam of gold-anodized parts, a front brake rotor
guard, Akrapovic muffler and D.I.D. rims, the
only significant difference between the current
2016 KTM 450SXF and the 2016-1/2 KTM 450SXF
Factory Edition V is the WP 48mm AER forks on
the Factory Edition V. There are some minor shock
valving changes, but nothing wholesale—just more
low-speed compression damping.
( 2) What does AER stand for? It is the Greek
word for air. More accurately, it is one of two
words that Greeks use for air. The other is aether,
but that is typically used to describe the upper
atmosphere above the clouds. AER is not an
acronym for a made-up technical jargon; it’s just a
way of spelling air without using the word air.
( 3) Unique forks. The WP AER forks are quite
unique in that they share very little with other
air forks on the market. In many ways they are
ingenious in their simplicity. Only the left leg is
charged with air, and that air is contained in a
sealed cartridge. The standard air pressure is 156. 4
psi—and KTM provides a pump with every Factory
Edition V. Unlike PSF or TAC forks that use either
a coil spring or separate balance chambers to
eliminate top-out, the WP AER forks work on the
same principle as a rifle. It used the compressed
air that is generated from fork movement to
dampen the fork on its return stroke. And, it
does this with no moving parts. Instead, the air
cartridge has a bump-out that works as a controlled leak when the 34mm cartridge rod piston
goes by it. Thus, in one up-and-down stroke, 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). The standard settings are 15 clicks out.
( 4) Verdict. Most MXA test riders felt that
the AER fork was a big step up from the current
4CS fork—this is especially appreciated by fast
Intermediate and Pro test riders who weren’t the
target audience of the 2016 WP 4CS setup spec.
The AER fork is much more resistant to bottoming
and very sensitive to clicks. Almost every speed
test rider, from Novice to Vet to Pro, stayed very
close to the 156. 4 psi air pressure and relied on
clicker settings to get the most out of the AER
fork. As for ballpark numbers, we think that a fast
rider will probably run 156. 4 psi with 18 clicks out
on compression and 18 clicks out on rebound. The
setting for an average rider would be 156. 4 psi (or
less), 28 clicks out on compression and 17 clicks
out on rebound. On the shock we ran 105mm of
sag, the high-speed compression turned out to
2-1/4 turns, and the rebound turned in a couple
clicks from stock.
( 5) AER problems. Air forks aren’t the same
as coil-spring forks. They follow the ground
differently, and most test riders prefer coil-spring
forks like Yamaha’s SSS Kayabas or WP’s Cone
Valve kit forks. That said, most of our complaints
about the WP AER fork revolved around getting
the fork to settle into corners without riding too
high. We tried everything from different race sag
to every air pressure setting in the book, which
allows a max of 217.6 psi and a minimum of 116
psi. We also had issues with the seat height of the
