What are PSF (Pneumatic Spring) SFF (Single Function) forks.

Video credit: Dirt Rider Magazine

Since the PSF (Pneumatic Spring Forks) became a reality, it has continued to evolve. Some of the early PSF forks are nearly identical to mechanically sprung twin chamber forks, with the exception that the springs have been replaced with air chambers. What you see here are PSF forks that are also SFF (Single Function) TAC (Tunable Air Chamber) forks. With SFF, one fork tube acts as the pneumatic spring and the other fork tube acts as the damping unit.

The video here shows the internal design of the PSF SFF TAC forks by showing and explaining actual cutaways of pneumatic spring forks mounted in a dirt bike. This excellent video will help you understand the PSF fork design regardless of model, but specifically shows forks for the following motocross bikes:

  • 2015 Kawasaki KXF450
  • 2015 Honda CRF250
  • 2015 Suzuki RMZ450


Internal design of the PSF SFF TAC forks. 4:34 minutes.

You might also be interested in my discussion about Understanding the springs.

In the article I talk about the differences between mechanically sprung forks and air forks.

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