Load Assist Airbag PSI: How to Set It Right in 2026
Setting load assist airbag psi correctly is what separates a level, stable tow from a vehicle that bounces, sags or bottoms out under load. This guide covers how to find the right pressure for your setup, your load and your towing conditions in 2026.
- Most load assist airbags operate between 5 psi and 100 psi — never run below 5 psi unladen or the bellows can unseat.
- Weigh the vehicle laden before settling on a final load assist airbag psi — guessing wastes air and wears the kit unevenly.
- A digital air pressure controller removes the guesswork of manual load assist airbag psi adjustments on the road.
- Bottoming out at maximum psi means the kit is undersized for the load, not that you need more air.
Why this matters
An underinflated airbag does almost nothing for rear-end sag. An overinflated one makes the ride harsh and can push more load onto the outer edge of the tyre contact patch than the vehicle needs.
Boss Air Suspension load assist kits, like the Ford Ranger and VW Amarok load assist kit, are designed to work alongside the factory suspension, not replace it. The airbag pressure is the adjustable part of that equation, and getting load assist airbag psi wrong undoes the benefit of fitting the kit in the first place.
Air pressure also isn't a fixed number. It changes with what's in the tray, whether you're towing, and how far you've loaded the vehicle forward or back of the axle. Treating psi as a one-time setting is the most common mistake owners make in 2026.
What you'll need
- An accurate tyre-style gauge rated to at least 100 psi (a low-range car gauge won't read correctly)
- A 12V compressor or hand pump capable of reaching your kit's rated maximum
- Access to a public weighbridge, or known weights for your load and towing setup
- Your vehicle-specific load assist kit fitted and the fitment instructions on hand
- A notepad or phone to record unladen and laden readings so you're not guessing next time
The steps
1. Confirm your kit's rated PSI range
Check the fitting documentation that came with your kit before you add any air. Most Boss Air Suspension load assist airbags are rated to operate between 5 psi and 100 psi, and running outside that range risks damaging the bellows or the mounting plates.
The rated range matters more than any single number you read online, because it tells you the ceiling you're working within for your specific vehicle and kit.
Common mistake: assuming every airbag on every vehicle uses the same working pressure. Fitment, spring rate and load all shift the ideal number.
2. Set a safe unladen baseline
With nothing in the tray or on the tow ball, set both airbags to a baseline of around 5 to 10 psi. This keeps the bellows seated against the mounting plates without adding stiffness you don't need for an empty vehicle.
Running zero psi for extended periods is not recommended. The airbag needs some residual pressure to sit correctly and avoid chafing against itself when the suspension cycles.
3. Weigh the vehicle with a full load
Load the vehicle the way you actually use it — full water tanks, camper trailer on the ball, tools in the tray — then get it across a weighbridge. This is the step most owners skip, and it's the one that actually tells you what pressure you need.
Compare the laden weight to your vehicle's GVM and axle ratings on the compliance plate. Do not use airbag pressure as a way to exceed those figures. Load assist airbags support the existing suspension; they don't raise the legal GVM or towing capacity of the vehicle.
4. Add air in stages and recheck ride height
Add air in 5 to 10 psi increments rather than filling to maximum straight away. After each stage, check ride height at the rear guards and compare side to side.
Stop adding air once the vehicle sits level and the rear hasn't sagged below its unladen height. For most utes and 4WDs carrying a moderate load, this lands somewhere between 20 and 60 psi, though the exact figure depends on the load and the kit fitted.
5. Road test under load
Drive the loaded vehicle on a mix of surfaces — highway, corrugated dirt, a speed hump or two. You're checking for harshness, bottoming out, and whether the vehicle tracks straight under braking.
A ride that feels too firm at speed but fine at idle usually means the pressure is a touch high for that particular load. Drop 5 psi and retest before committing to a number.
6. Fit a gauge or digital controller for repeatable settings
Manual valve caps work, but they make it easy to lose track of what pressure is actually in each bag. A digital air pressure controller lets you read and adjust both airbags from the cab, which matters when you're switching between an empty run and a fully loaded tow in the same day.
This is also the easiest way to keep left and right pressures matched, since uneven psi side to side is one of the most common causes of a vehicle pulling to one side under load.
7. Recheck after the first 500km and each season
Air does bleed slowly from fittings and valve stems over time. Check pressure again after the first 500km of towing, then build a habit of checking before long trips.
Temperature swings between summer and winter in 2026 will also shift pressure slightly, so a psi that felt right in January may need a small adjustment by July.
Troubleshooting
Vehicle still sags at maximum rated psi. The kit is likely undersized for the load being carried. Check a vehicle-specific load assist kit rated for your actual laden weight rather than pushing pressure past the rated ceiling.
Ride is harsh with nothing in the tray. Drop back toward the 5 to 10 psi unladen baseline. Airbags don't need much pressure to do their job when the vehicle is empty.
Uneven ride height side to side. This is almost always a pressure mismatch between the two airbags rather than a fault with the kit. Rebalance both sides to the same reading with a reliable gauge.
Slow air loss overnight. Check the valve stem and fittings with a soapy water test before assuming the airbag itself is faulty. A slow leak at a fitting is far more common than a bellows failure.
Airbag bulging oddly at one point. Stop adding air and inspect for interference with a bracket, shock or chassis rail. Continuing to inflate against an obstruction can damage the bellows.
Gauge and controller disagree. Cross-check both against a known-accurate reference gauge. A cheap analog gauge drifting by 5 to 10 psi is common and will send you chasing a number that isn't real.
Tools and resources
- A rated gauge and 12V compressor, checked against each other periodically
- An airbag fitting kit if valve stems or lines need replacing during a psi check
- A digital air controller if you're switching loads often and want repeatable settings without crawling under the vehicle
- Your vehicle's compliance plate, for GVM and axle rating reference
What to do next
If you haven't picked a kit yet, working out the right psi range starts with matching the kit to the vehicle and the load first. The guide on how to choose the right load assist airbag kit covers fitment, lift height and load ratings in more detail before you get to setting pressure.
FAQ
What PSI should load assist airbags run at?
Most Boss Air Suspension load assist airbags run between 5 psi unladen and up to 100 psi rated maximum, with the actual working pressure set between those points based on the load carried. The right number depends on laden weight, so weigh the vehicle before settling on a final pressure.
Is it safe to run load assist airbags at 100 psi?
Running at 100 psi is only appropriate if the kit is rated for it and the vehicle is carrying a heavy enough load to justify it. Running at maximum pressure with a light load produces a harsh ride and offers no benefit.
Do load assist airbags increase GVM or towing capacity?
No. Load assist airbags support the existing suspension and improve ride height and stability under load, but they do not raise the vehicle's legal GVM, axle rating or towing capacity unless paired with an approved GVM upgrade.
Can I run different PSI in each airbag?
Small differences of a few psi can happen with uneven loads, but both airbags should generally be matched to keep ride height level side to side. A consistent gap of more than 5 to 10 psi usually points to a leak or gauge error.
How do I check airbag PSI without a gauge?
You can't reliably check load assist airbag psi by feel or eye. A rated gauge is the only accurate way to know what pressure is in the bag, and cheap gauges can drift by 5 to 10 psi.
What happens if PSI is too low?
Running below the recommended 5 psi baseline for extended periods can let the bellows fold or chafe against the mounting plates. Too little pressure also means the vehicle keeps sagging under load, which defeats the purpose of the kit.
Should airbag PSI change between towing and carrying tools?
Yes. Towing a trailer or caravan usually shifts weight differently than a tray full of tools, so the ideal pressure often changes between the two. Check ride height each time the load type changes significantly.
How often should I check load assist airbag PSI?
Check before any long tow, after the first 500km following a pressure change, and again each season as temperature swings can shift readings slightly. A quick check takes a few minutes with a rated gauge.
One last thing
Most pressure-related issues with load assist airbags in 2026 trace back to under-inflation, not over-inflation. Owners tend to be cautious about adding air, then wonder why the rear still sags under a full tow load. Start light, weigh the vehicle laden, and add air until the ride height sits level rather than guessing at a round number.
