Firestone Coil-Rite

Helper airbags

LandCruiser 200

Step-by-Step installation

When choosing suspension for your vehicle, there is often a tradeoff between handling and performance when laden versus unladen.

If you fit rear springs that deliver comfort and a correct ride height when the vehicle is unladen, then it will result in sagging when you load up for a trip. Conversely, if you fit heavier springs to cope with high loads, then it will mean a harsh ride and tail-high vehicle once you're unladen between trips.

Helper airbags

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 model, but you may also be able to use the shorter (9") 4114 or the longer (11") 4129 if you can't get the 4164. The size you choose depends on the suspension you have fitted, and determines the amount of bump stop that is removed during the fitting process. See the steps below and the video for details. If you prefer the red bags, the Airlift kit (9.5" long) would be the 60750, or the local Polyair kit is the 15095 for raised suspension, or 15895 for standard suspension.

When it comes to actually purchasing the airbags, you'll find that (unfortunately) they are an item that usually costs substantially more to purchase locally than overseas. Typically, the retail price at the time of writing for both Firestone and Polyair bags in Australia is almost double the price of buying the same products from the US. If you're looking for a local supplier for the Polyair bags, Air On Board sell them somewhat cheaper than other local dealers.

Amazon Update 15/7/16: Because Amazon is an 'open marketplace', where you can buy something either from Amazon itself or other dealers operating in their marketplace, it can be a challenge to find an item from a dealer that ships to Australia. It's difficult to create a link to a particular item from a particular dealer on their website. This link should direct you to the bags being sold by Amazon directly, where you can see if international shipping is offered.

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.




4164

IMPORTANT

The "Installation" section should not be taken as instructions. It is simply a documenting of the procedure I followed for my own installation. No warranty is provided as to the accuracy of the information, and/or whether it applies in your situation or to your vehicle. If you're not qualified and/or don't have the correct equipment, get the airbags fitted professionally.

  • There are potentially lethal dangers involved during the installation from falling vehicles or components and/or component or equipment failures.
  • There are potentially lethal dangers resulting from failure due to improper installation.
  • There is the potential for expensive vehicle and/or suspension damage from improper installation.

If you undertake your own suspension installation, you do so entirely at your own risk.

Equipment required 

  • Assorted spanners and sockets
  • torque wrench
  • A sharp knife (for cutting air lines)
  • Tek screws
  • Touch up paint
  • Thread locking fluid (eg Loctite 243 or 263)

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Installation

Click images to enlarge

Step 1:

  • 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.




Step 2:

  • 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.

NEVER work under a vehicle that is supported by a jack (or jacks) alone.

Step 3:

  • Remove the diff breather hose, and remove the bolt holding the brake lines 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.

Step 4:

  • Remove the springs from each side, complete with the internal bump stops. You then need to cut the bump stops to the appropriate length for the #4164 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), use #4129 airbags instead of #4164, and cut off three segments.
      Ensure you remove any burrs from the cut edge of the bump stop.

Using shorter or longer airbags:

  • It is also possible to use the shorter #4114 airbags with standard suspension, if you cut three segments off the bumpstop instead of four.
  • It is also possible to use the longer #4129 airbags with 20-50mm lift suspension, if you cut four segments off the bumpstop instead of three.




Step 5:

  • 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.

Step 6:

  • 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 7:

  • 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 8:

  • 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 9:

  • 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.

Step 10:

  • 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 11:

  • 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.

Comments / Q&A