Nitrogen Pressures for Different Applications
Nitrogen pressure in a smooth body or coil over shock is used to prevent cavitation of the oil as the piston speed and forces increase. It is not used as a tuning method. Ride quality should be tuned with spring rate and piston valving. For all standard ADS bolt on components, the nitrogen pressure should be set to 150 PSI at full extension. Race applications will vary from 150-200 psi. Please contact our technical support team for more information on tuning for race applications.
Air shocks and bump stops use nitrogen to generate spring force as well as activating the seals. This is possible with its large shaft displacement and minimum volume for the nitrogen when fully compressed. Nitrogen’s pressure exponentially increases as the volume gets closer to zero due to the ideal gas laws. If you review the data, you will find that every time you reduce the volume by half, it doubles the psi. Here is an example; A 10-inch travel air shock that has nearly no volume for the nitrogen is fully compressed. In other words, it has maximum oil volume before hydro locking.
| Inches of Shaft Showing | Nitrogen PSI | Nitrogen PSI | Nitrogen PSI |
|---|---|---|---|
| 10 (Base Pressure) | 150 | 200 | 300 |
| 5 | 300 | 400 | 600 |
| 2.5 | 600 | 800 | 1200 |
| 1.25 | 1200 | 1600 | 2400 |
| .75 | 2400 | 3200 | 4800 |
| .375 | 4800 | 6400 | 9600 |
Looking at the chart, you can see how your original nitrogen pressure dramatically changes as it’s compressed. Keep in mind that this shock has maximum oil capacity. You can reduce your oil level to keep the pressure from ramping up so quickly. If there’s too much oil in an air shock, it cannot completely compress and it could damage the system. An easy way to check if it will hydrolock is to bleed out all the nitrogen and see if you can fully compress the shock on the bench. Keep in mind that air shocks are emulsion shocks, so the nitrogen gets mixed with the oil and creates lots of bubbles. All the bubbles will try to come out when you’re compressing the shock so sometimes letting it sit vertically at full extension with the air fitting on top will let them settle down.
To set ride the height of a vehicle with air shocks you will need a nitrogen tank with a pressure regulator and a way to lift the vehicle and get the shocks at full extension. The pressure will increase or decrease your ride height as you increase or decrease the pressure. A good starting point is 150 PSI at full extension. The operating range is 75-250PSI for air shocks and bump stops.