Tuning Rock Shox Dual Air Forks
- The sum of the pos/neg pressures relates to the fork's actual spring rate.
- Why? Because Hooke's Law is counter intuative at times. Stacking springs reduce the system rate, opposing springs increase the system rate. This has nothing to do with equalibriam or the forces, just how the forces will change with displacement. While the pressures and forces at each side of the fork will change, since they are constantly in interplay with the air spring system, they will always be increasing the rate of the system.
- The pos/neg distribution adjusts ride height.
- Make sure to remove all the spacers from inside the fork. Use pos/neg air Distribution to adjust the bump travel.
HERE'S THE TRICK:
- Fill the forks with air with two pumps and gauges. One side effects the other, so you have to do them both at the same time to get predictable results.
- The goal is to have both pressures the same, but this may not be possible if the geometry of the bike needs additional adjustment with ride height. If the pressures are way off, you may need a longer or shorter fork.
- Use positive to adjust springs at the bottom of travel
- Use negative to adjust ride height.
- Subtle changes in oil volume on the damper side makes a huge difference in bottoming feel.
What Rock Shox Says
Make sure to set the floodgate to the lowest setting that produces a solid pedaling platform. The fork should be active over any bumb in the trail. Many people make the mistake of setting this feature way too high.
Rebound should be set to provide the plushest 'feel' on rough singletrack. The forks should not feel harsh as that would mean that you have too much (packing) or to little rebound (spiking).
The stock damping fluid on 2007 Rock Shox products is Maxima 85-150 Fork Fluid. The ISO viscosity of this oil is 15.90, a good starting place for any fork either motorcycle or bicycle.
I tend to replace fork fluids with Red Line Suspension Fluid. 28% Red Line (Extra Light,Blue) & 72% Red Line (Light,Yellow) will duplicate ISO 16.
Other damping and lubrication options are provided by '15wt (Stock)' oil. Assuming that they are using Maxima for this as well, then the viscosity of this would be ISO 46. Red Line equivilant is 57% Red Line (Medium,Red)& 43% Red Line (Heavy).
Subtle changes in volume on the damper side will make a huge difference.