Firestone Coil-Rite
Helper airbags
LandCruiser 200
Step-by-Step installation
Note that this article has been superseded. I have now replaced the standard Firestone airbag kit with a Heavy Duty kit, offering higher pressures for higher load capacity, superior damage protection and in-cab air control and pressure monitoring.
Read the new article and install guide here
Firestone coil-rite airbags for a LandCruiser 200
One of the most common solutions to this problem is to fit polyurethane 'helper' airbags, which are installed within the rear coil springs.
When the vehicle is unladen, the airbags are set to minimal air pressure. But when loaded for a trip or towing a caravan or camper-trailer, the pressure is increased in the bags allowing the vehicle to carry higher loads while maintaining the correct ride height.
Pros and Cons of fitting helper airbags
The main benefit of fitting helper airbags instead of different coil springs is that they allow for variable loads. You don't have to choose between having a vehicle that sits high and rides poorly when unladen, or one that sags and bottoms-out when laden. You can have the best of both worlds.
But nothing is without compromise. The airbags do reduce suspension travel slightly, particularly when they are inflated. This is more a concern for vehicles set up for hardcore weekend 4WDing than touring vehicles, but still something to be aware of.
Additionally, while airbags are very durable, they're not as strong as a steel spring and are therefore more susceptible to damage. In the case of failure you would lose the benefit of the bags, leaving you with a saggy rear end....and nobody wants that! If you're particularly concerned about damaging the bags, you can buy Kevlar sleeves to provide greater protection.
Selecting and buying airbags
There are two major brands of helper airbags on the market, being Firestone and Airlift (sold as Polyair in Australia). The Firestones are blue while the Airlift/Polyair bags are red. Other than colour, there's little difference between them in price, capacity or quality. Speaking to people with both brands, there seems to be nothing between the brands for durability, so it's likely that either will serve you well. They are all made in the USA from heavy duty polyurethane.
In most cases, the best choice in the Firestone bags is the 10" 4164
for raised suspension, or 15895
for standard suspension.
Using and inflating the airbags
The Firestone Coil-rite airbags can be inflated up to 240kPa (35psi), depending on the load. You must keep a minimum of 35kPa (5psi) in the bags at all times to prevent them being pinched and damaged by the coil springs.
The standard kits include basic 'tyre' inflation valves. Because I already have an on board air compressor and reservoir, I'll be hooking my airbags up to that via an Air On Board control panel, which includes a dual-needle pressure gauge and fill valves for each bag.
Installation
Note that while the video and tips below are shown on a LandCruiser 200, there is very little difference between the 200 and earlier 100/105 and 80-series LandCruisers when it comes to installing the bags.
- A quality trolley jack
(Min 1800kg rating, Min 450mm lift)
- A pair of chassis stands
(Min 1800kg rating)
- A reciprocating saw or hacksaw
- A drill with a ~35mm holesaw
- Flat and phillips screwdrivers
- A 5mm allen key (for KDSS vehicles)
- Assorted spanners and sockets
- A torque wrench
- An airline cutting tool or sharp knife (for cutting air lines)
- Silicone sealant
- Thread locking fluid (eg Loctite 243
or 263
)
Firestone Coil-Rite Installation
Click to Enlarge
Step 1 - Prepare the vehicle:
- If your 200 has KDSS, then release the two shutter valves 3 turns.
- Raise the vehicle so the rear wheels are off the ground, and support it on chassis stands. Leave the jack under the diff centre, so you can raise and lower the axle as required during the installation.
- Remove both rear wheels, and place them under the chassis for extra safety when you're working under the vehicle.
- With the jack taking the weight of the axle, remove the bottom mounting of both rear shocks, and the sway bar brackets on each side.
- Remove the diff breather hose and remove the bolt holding the brake line bracket to the axle, just above the differential. This will allow the axle to drop without straining the breather/brake lines.
- Lower the axle on the jack until the springs are loose.
- Remove the springs from each side, complete with the internal bump stops.
NEVER work under a vehicle that is supported by a jack (or jacks) alone.
Click to Enlarge
Step 2 - Cut bumpstops to suit:
- Cut the bump stops to the appropriate length for the Firestone 4164 or PolyAir 15095
air springs, as per the photo:
- For Standard suspension, cut off 4 segments;
- For 20-50mm lifted suspension (eg: Tough Dog, OME, Lovells etc), cut off three segments;
- For 60-75mm lifted suspension (eg: ICON, Fox etc), cut off two segments.
Ensure you remove any burrs from the cut edge of the bump stop. for raised suspension, or for standard suspension.
Using shorter or longer airbags:
- It is also possible to use the shorter PolyAir 115895
airbags with standard suspension, if you cut three segments off the bumpstop instead of four.
Step 3 - Install fill valves/panel:
- Work out where you plan to mount the fill valves, or (as in my case) the AOB control panel. In my case, the AOB panel is located within the jack storage area in the lower-right of the load area.
- Cut the included air line tubing to suit the location of the valves/panel and the routing of the air lines. I cut the airline so the left side was 1/2 metre longer than the right.
- See Step 7 below for the valve panel mounting and connections.
Step 4 - Install airbags into coil springs:
- Slip the included protective sleeves over the ends of the airlines (at the bag ends).
- Thread the lines through the cut-down bump stops, then push them fully into the airbags.
- Slide the airbags into the tops of the springs, followed by the cut-down bump stops.
Step 5 - Install the springs and airbags:
- Thread the other ends of the airlines up through the chassis spring-locating holes on each side, then re-insert the spring-bumpstop-airbag assemblies into position, ensuring they are properly located at both the top and the bottom.
- Lift the axle back up on the jack, and reconnect the breather hose, brake line bracket, shock absorbers and sway bar mounts. Use Loctite on all the nuts and bolts.
- Refit the wheels and lower the vehicle back to the ground.
- Tighten the KDSS shutter valves
Step 6 - Run the airlines:
- Run the air lines to the location of the control panel/fill valves, ensuring you cable-tie them regularly and keep them away from sharp edges and the exhaust.
- In my case, I ran the hose from the left side across the cross-member just behind the axle, until it met the other air line. Then ran them together along the right side chassis rail towards the rear of the vehicle, then up through a slit in the existing wiring grommet into the jack storage area.
- Put a band of red electrical tape around the "right" side hose, so once the lines are together it's simple to identify which hose belongs to which side.
- Ensure you seal the slit cut in the wiring grommet with some silicone or polymer sealant.
- If you're using the AOB control panel and on-board compressor, then run an airline from the compressor/reservoir to the control panel location.
Step 7 - Mount and connect the inflation panel (if used):
- I mounted the panel vertically to the steel inside the front of the cavity using tek screws. To do this, you must first remove the paddle switches from the panel.
- You can then connect all the airlines to the panel:
- Connect the line from the reservoir/compressor to the air inlet T piece.
- Connect the airlines from the bags to the included T pieces at the rear of the paddle switches.
- Note that I added another pair of T pieces so that the bags can also be inflated/deflated via the original tyre inflation valves. This is a handy backup in case the on board compressor fails.
Step 8 - Check for leaks:
- Inflate the airbags to ~30psi and check for leaks by watching the gauge needles and spraying the air fittings with soapy water, looking for bubbles.
Air leaks and adding shutoff valves:
The only drawback of the control panel is that adding so many fittings to the system makes air leaks far more likely. Instead of there being just two potential leaking fittings per bag with the standard tyre valves, the addition of the control panel means that each bag line has nine potential leak points.
Because the bags don't hold a large volume of air, even a very small leak can be an issue and I found it impossible to totally eliminate leaks. To overcome this, I added a manual shutoff valve in each bag's airline, between the bags and the first fitting for the control panel. This drops each bag line back to two potential leak points. The valves are usually left closed, and only opened when I want to inflate/deflate or check the bag pressures.
The valves are available on special order from Pirtek or Enzed for about $40 each (Yes, this seems excessive!). Note that all the fittings and airlines in the system are 1/4" imperial, not 6mm metric.