Motocross is going through a dynamic shift in suspension technology. Concepts that were way ahead of their time—like the Fox Air Shox and Factory Forx from the mid-1970s—are now viable options due to progress in technology and manufacturing.
Two of the latest suspension systems that have made headlines are Showa’s Separate Function Fork (SFF) as used on the Suzuki RM-Z450 and the brand-new KYB Pneumatic Spring Fork (PSF), which is fitted to the 2013 Honda CRF450R and Kawasaki KX450F.
While SFF separates the spring into one leg and damping duties into the other, the PSF does away with springs altogether. Here is a closer look at the PSF and its alleged benefits.
[ 2013 KYB Pneumatic Spring Fork (PSF) ]
Less work: Reduced weight means more-efficient damping circuits, allowing transitions from compression to rebound to happen more quickly, keeping the tire on the ground for improved traction.
Better feel: A larger, 32mm cartridge-damper piston (was 24) can now be used with the extra internal space made availble without springs. End result is improved feel throughout the stroke.
Linear feel: A balance spring helps make the air spring more linear as it extends by countering the rebound force.
Less friction: An anti-friction coating called Kashima is applied to the stanchions to reduce stiction.
Lighter: Eliminating the steel springs (2012 KYB Fork pictured above) resulted in a reduction in sprung mass of almost two pounds. Air costs less than steel.
Bottoming resistance: More internal space allowed a larger-diameter bottoming cone to be used. When combined with the air fork’s progressive nature, this makes the PSF more forgiving.
No special tools: Air adjustments can be made with any pump that fits a Schrader valve.
User friendly: No spring changes necessary to optimize fork for rider weight and preferences. Simply adjust air pressure (pictured below).