Air Suspension for Towing
The suspension is one of the hardest things to get right in a 4×4. Most of us use our vehicles as both daily drivers and adventure machines, and air suspension is one of the best ways to adjust to suit the weight of these varying loads.
While we often have a similar rear loading problem when not towing, connecting a camper, caravan or boat is especially challenging as the ball weight of what we are towing is attached to the rearmost point of our vehicle. It’s a weight we can’t pack forward to balance the 4×4, so it’s all loaded on the rear suspension.
Combine the ball weight of what your towing with your usual loads – people, fuel, water & gear – and the rear of most vehicles is likely to droop.
Does Being Back Heavy Matter?
While vehicles sagging in the back end might not look as pretty in pictures, there is more to it than that.
Safety is always my number one. I take responsibility for the setup of my Cruiser and loads, and I don’t want my loved ones, mates or other road users to get hurt by my choices. Braking and steering work on a balanced vehicle. If we are overloaded, we change the geometry; the steering lightens, and the braking is less effective. Small things like our headlights pointing into the eyes of other drivers’ eyes impact on safety too.
It’s not just safety that’s an issue either. Off-road overloaded shock absorbers struggle to compress and rebound. The ride is uncomfortable and because less shock is absorbed the impact on numerous components of our vehicles is more significant, which can lead to a remote breakdown or the premature need to replace parts.
Air suspension is perfect for towing as it allows for quick adjustment to make the suspension firmer when you hook up your camper, caravan or boat.
If you’ve bought one of the new Land Rover Defender’s, you’ll have air suspension ready to go out from the factory. For most of the most popular 4x4s though, it’s an aftermarket upgrade.
If you are looking to upgrade your suspension, we’d recommend a Gross Vehicle Mass (GVM) upgrade too. Unfortunately, for most travellers, it’s almost impossible to keep below the factory GVM weights with the extra fuel, water and gear needed for travel plus the ball weight of what we are towing.
We also recommend adding air suspension in the rear. In our LandCruiser 76 Series, we upgrade the GVM to 3,660kg. The rear suspension is a leaf plus shock absorber setup, and we had the option of 400kg, 600kg or 800kg constant load leaf suspension. The 76 Series is my daily driver, so I take lots of gear out between trips but leave in my drawers, fridge and some equipment. I opted for the 600kg leaf pack, and it’s comfy around town, but not quite enough with full loads and towing. The 800kg option would have worked at maximum loads, but it also would have been uncomfortable around town and stiff off-road.
In our 76 Series, we have what’s called an Airbag Man Helper Kit. A substantial airbag sits on each side of the rear axle and helps the suspension. With heavy loads, we air them up; it’s kind of like taking the leaf suspension from 600kg up to 800kg rating. Around town, we let air back out again for comfort.
For coil spring vehicles Airbag Man offers a similar setup, but this time the airbag sits inside of the coil. They also, provide full coil replacements for some cars like the 200 Series LandCruiser.
While we recommend the Helper Kits, make sure you use them within the recommended pressure range. If you skimp on upgrading the rest of your suspension to suit your loads and instead fit and over-inflate airbags, they will be rock hard. Over-inflated airbags will make for an uncomfortable ride, and it may damage your vehicle too, especially in utes with the tow ball a long way back from the rear axle.
You can fit coil-sprung camper trailers with airbags too. The geometry can change quite a bit with full water and gear. The airbags help the suspension and can also aid in ensuring the tyre camber remains correct.
Adjusting to Suit Tow Loads
With your camper, caravan or boat connected to a 4×4 with a good setup suspension adjusting is easy. It’s a simple matter of adjusting the pressure in the airbags until the vehicle is level.
In our Cruiser, we have fitted switches in the rear. We flick on our onboard compressor and simply toggle the switches.
Airbag Man offers two other options. The first, a wireless controller which is the easiest of the options. They also offer manual inflation points which easily mount on the tow bar. These points are tyre valve sizes so can be operated with your standard compressor, tyre gauges and deflation tools.
You’ll likely learn your go-to pressures pretty quickly, but you may need to adjust for more significant weight variations like empty supplies and water tanks at the end of a trip.
For more technical information, visit Airbag Man.