Change the spring rate of the Fox Float RP air shock in three minutes with the new Float Volume Spacer kit.Change the spring rate of the Fox Float RP air shock in three minutes with the new Float Volume Spacer kit.
Air-sprung shocks can be tuned to work with a relatively wide range of rider weights. That said; there are instances when an air spring cannot be satisfactorily tuned because a rider is too heavy for a particular suspension design, would like to use less air pressure without bottoming the suspension, or may want the shock to perform outside of the limitations imposed by the volume of its stock air canister. The Fox Float Volume Spacer kit allows you to tune your air-shock's spring rate inexpensively and without tools. Before we show you how to install a volume spacer into an RP 23 shock, we'll go over the spacer kit and cover a few tuning tips so we all start on the same page. The Fox Float Volume Spacer kit:
Taking a cue from aftermarket suspension tuners, Fox Racing Shox developed an internal Volume Spacer kit for its RP-series shocks that changes the compression ratio of the air spring. The kit includes three plastic spacers that snap onto the shaft inside the air canister. The spacers reduce the air volume of the air-spring chamber, causing the pressure to ramp up faster as the shock compresses. In case you wanted to know, the volume changes for each spacer are, .2, .4 and .6 cubic inches, and installation can be done with a shock pump and a small screwdriver in three minutes. What you'll need to do the job:
• A clean shock and a clean environment to work on it
• A good shock pump
• Fox Float Volume Spacer kit ($24.99 USD, Fox part #803-00-612
Fox Volume Spacer kit includes .2, .4 and .6 cubic inch plastic spacers that snap inside the RP23 shock's air-spring chamber.
Why Change the Shock’s Compression Ratio?
Fox Racing Shox developed the air-sprung Float RP 23 and its near relatives to be the most versatile shock made. The debut of its volume spacer kit gives rank-and-file riders an inexpensive tuning tool that previously was a professional-only option.
Before we get started, a brush-up on air springs and spring rates may be helpful. Unlike a coil spring, which retains zero energy while uncompressed, an air spring begins at a high, pre-set static pressure. Preload adjustments to change suspension sag do not affect a coil spring’s overall rate, but any changes in air pressure will alter an air shock’s suspension-sag measurement and its overall spring rate at full compression. Because sag and spring rate are bound together, a rider who pumps an extra 50 psi into the air can in order to prevent harsh bottoming must also suffer a harsh ride in the initial suspension travel and a taller ride height due to reduced shock sag.
Suspension tuners separate the sag and spring-rate functions of an air shock by changing the volume of its air can. Reducing the volume of the air chamber causes the air pressure to ramp up quickly, so the spring pressure can be set low, allowing more suspension sag without risking harsh bottoming. A larger-volume air can ramps up less at full compression, but the shock will sag less because more volume requires significantly higher starting pressures to prevent bottoming at full compression. Fox’s internal spacers allow riders to change the volume of the air spring and fine-tune the spring rate of the shock without replacing the expensive air can, or even removing the shock from the bike. Read on and Pinkbike will show you how it's done.
How to Install a Fox Volume Spacer
Jim (Master of Stone) Noonan powers up "the Staircase" on Chumash Trail. Jim came down from the Fox factory in Watsonville, California, to talk 2012 suspension, ride bikes and show us the new Volume Spacer kit.
Fox’s Jim Noonan visited Pinkbike to give us the blow-by-blow on their new air-volume spacer kit. Jim says the whole process can be done by hand, with no tools beyond a shock pump. To prove how simple a task it is, we installed the spacers in the trailhead parking lot. That said, he recommends that the work be done in your home environment because it is imperative that no dirt or grit be introduced into the inside of the shock.
Step one: Release all pressure from the shock. Depressing the Schrader valve with a small Allen Key or screwdriver makes this easy.
Step two: The Air Can is threaded to the top of the shock body. Grab it firmly and twist it clockwise (right to left) to unscrew it. The force of the shock's negative spring will keep the can pushed up against the threads. It is important not to yank down on the can at this moment.
Step three: Carefully slide the air can down the shock body. As the lower seal of the air can reaches the end of the shock, the negative spring will abruptly switch off. Stop right before the can's air-seal slips off the shock and the can will remain in place. Check to see that the can will stay put before you release it.
Step four: Look under the air-chamber head for an O-ring and a steel washer (as pictured, there may be a white plastic air-volume spacer up there also). Use your fingernail or a thin screwdriver blade to slide the O-ring and washer down the shock shaft. If needed, pop the spacer out and pull it off of the shaft
Step five: Choose one of the three spacers, slip it over the shaft with the recess facing down and then slide it up until it snaps into the upper shock head. Slide the O-ring and washer up until they nest into the spacer
Step six: Grab the air can securely with one or two hands and ease it back upwards until it GENTLY rests against the threads of the air can head and then screw it in counter-clockwise (Left to right) until it tightens snugly with moderate hand pressure. Take care on this step not to lose control of the can when the negative spring engages because the sudden acceleration will slam the can into the threads of the sealing head and can damage the shock.
OK, that’s all there is to it. Contact Fox Racing Shox to learn more suspension setup tips in its uber-informative tech section. If you have any Fox air-spring tips to share, we’d love to hear from you.
Step seven: Inflate the shock to your normal pressure first. Take the bike out for a short test run to establish a base-line setting before you begin experimenting on new shock-spring pressures.
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