It’s easy to see the difference between KYB’s conventional MX fork (left) and its new PSF design (right): one has a spring, the other doesn’t.
WORDS: Aaron Frank
Air suspension isn’t anything new. As recently as the 1980s, sportbikes used compressed air either as the springing medium or to assist a conventional coil spring. Heck, certain Victory and Kawasaki cruisers use air shocks today. Performance issues including increased stiction, big-hit blowouts and a changing “spring” rate as the suspension heats up have so far limited the usefulness of air shocks for racing or other high-performance applications.
Until now: Advances in materials and manufacturing processes have reportedly eliminated these potential problems, leading Japanese suspension giant Kayaba (KYB) to develop the all-new Pneumatic Spring Fork (PSF) that debuted on the 2013 Honda CRF450R and Kawasaki KX450F motocross machines. Kayaba says the advantages are significant. Replacing coiled-metal springs with a column of air reduces unsprung weight nearly two pounds, and makes fine-tuning spring preload as easy as adjusting the air pressure in your tires, via a Schrader valve mounted at the top of the fork leg.
Deleting the springs makes room for a bigger piston, expanding from 24mm to 32mm to provide more precise damping response. Initial impressions have been positive, with riders across the age and experience range—including ex-editor Catterson—praising the PSF for exceptional stability and small-bump compliance. If air shocks fly on the high-flying MX circuit, look for this weight-saving technology to “revolutionize” sportbike suspension next.