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AIR FORKS good, bad or ugly!

Updated: May 7

Let's start with friction and stiction, and find out if air forks are good, bad or ugly.

Stiction is the static friction that needs to be overcome to enable movement of two stationary objects in contact with each other.

Imagine a heavy equipment loader/tractor, when it lifts a large load of dirt the pressure inside the ram when lifting expands the seals against the chrome tube. 

Without that added pressure the hydraulic fluid would blow right by the seals. 

The pressure expands the seals by design and they squeeze the chrome tube so tightly that they hold back massive amounts of pressurized hydraulic oil.

The seals on your forks use the same seal design to keep the fork oil contained.

Both air forks and spring forks increase the internal air pressure when the forks compress. 

Hydraulics versus Motorcycle forks

  • Air forks have high air pressure even when the forks are all the way up or fully extended. 

  • Spring forks have zero psi when fully extended.

  • Air fork's high psi expands its seals much tighter than the spring fork.

  • Tighter seal makes it harder to get the fork to move due to increased friction and stiction. 

  • Both stiction and friction reduce compliance, plushness, cornering feel and comfort.

If you ride through a rock garden on the air forks the added friction from the seals against the chrome tubes will not allow the forks to move freely as a spring fork does. 

Some of the air forks do have features to mitigate this with negative air chambers etc.

These attempts to alleviate the issue does not, as of yet, get them into the realm of the spring forks.

  • Air forks huge increase in pressure at the bottom of the stroke makes them highly "Progressive".

  • Spring fork in comparison will give you a much more consistent increase in rate as you compress the forks to the bottom making them much more "Linear".

Air forks progressive spike in spring rate effects rebound.

The very high spring rate at the bottom of the air fork stroke will overpower the rebound circuit until the forks extend and lighten up the air pressure or spring rate. 

Therefore when you go deep into the stroke the forks tend to have an initial aggressive bounce back with less control. 

Spring fork, with its linear spring rate, allows that same rebound event to be more controlled, more consistent, smooth and comfortable.

Again, "Linear".

  • When built a professional rider can win national level events on the air fork!

  • The harder and faster you hit obstacles the more compliant your components become. That said if the rider backs off the pace just a bit then the fork will show its lack of compliance causing increased fatigue and more.

  • Air forks are lighter weight.

  • Air forks are less money to build.

Dave Johnson,

A brilliant Suspension engineer in the San Jose / Silicon Valley area designed an air fork with an ECU, internal diaphragm air compressor capable of adjusting air pressure every millisecond. Although viable mechanically, the cost to complete the engineering was prohibitive.

Would this help alleviate the stiction issue?

Possibly deep in the stroke, by lowering the psi it would have made the fork more linear, in addition to a reasonable amount of rebound needed for control. 

Think about this though. ECU forks could have memory. Knowing a track, firming up in the whoops and softening in the corners. That could reduce lap times! That could be big.

One last note. 

Progressive sounds good and sells to the less informed, but the reason manufacturers changed from damper rod forks to shim stack forks is to achieve less progression.

A vintage damper rod fork's spike, in a high speed compression event, is far is too "progressive".


Sound familiar?



When we put a build out, it will out perform nearly if not every re-valve in the nation or we test and improve unit it does. "Then" we offer the build to our customers. Look at the reviews!

The AER forks have the same tubes as WP's spring forks.

The AER forks have the almost exactly the same base valve as the 2024 Xact cc WP forks.

We turn the above components into one of the best forks in the world.

First we spring the forks to omit the stiction issue.

We design custom base valves so you can Re-Valve your forks in a few seconds. Gobblers!

We are the only company in the world to achieve this technology.

We back every in house build with a money back guarantee.

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