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Spring loaded – Tough Dog air Assist springs installation


Air helper springs are an often misused and misunderstood addition to a 4×4’s suspension system. Consisting of an extremely strong rubber air bag and bracketry, air helper springs are fitted to a standard vehicle’s rear leaf or coil springs to help the stock setup carry extra weight without upgrading the coils or leaf springs.

With that in mind, we took our long-term Isuzu D-Max to Opposite Lock in Wellington to have a set of Tough Dog Air Assist springs fitted. When looking into installing a set of air assist springs, it’s important to realise that they are not designed to replace the need for an aftermarket suspension system if your vehicle is consistently heavily loaded. Air assist springs are primarily designed to keep a vehicle level while towing or carrying the occasional load, while also improving stability and reducing stress on your rear coil or leaf springs. The beauty of air assist springs is that they can be adjusted to deal with different loads. As loads increase, air is added, and when the vehicle is empty, air is let out, so the ride is not overly firm.

During a recent trip to Malawi, our heavily-loaded Hilux relied on its air helper springs to keep it from bottoming out in the harshest terrain. With over 800kg loaded, the air assist system proved an invaluable accessory to our trip that would otherwise have required an entirely upgraded rear suspension – an expensive solution for just one trip.

Our Isuzu install

During our tenure with our long-term Isuzu, it’s been driven by a variety of different people over a variety of terrain. It is used for everything from 4×4 trails, to overland expeditions, to pulling heavy caravans, and simply going to the shops empty. For this reason, air helpers are perfect for our application due to the varied loads it is tasked with carrying. Tough Dog air bags are made from polyurethane and are designed to withstand up to 4-bar pressure, but as we’ve found in the past, even with almost one ton of load, no more than 1.2-bar is needed to level the vehicle. It is recommended that a minimum of 0.3-bar is kept inside each air bag.

The kit for a leaf-sprung vehicle comprises the air bag that is attached to a base plate and a similar steel plate on the top, which bolt to their respective brackets on the chassis and on the top of the leaf spring pack. The fit and finish of the laser-cut, powder-coated brackets is superb. Fitment at Opposite Lock in Wellington took just two-and-a-half hours and included fabricating a custom bracket to take the two air hose outlets, which enable each air bag to be separately inflated. Standard tyre valves are used, making it quick and easy to inflate, deflate or simply check the pressure in each air bag.

The Tough Dog leaf spring kit costs R11 295 (excluding fitment) from Opposite Lock. Peace of mind comes from a 3-year unlimited-kilometre warranty. For coil spring applications, an air bag can be fitted within the coil itself, making Tough Dog air helper springs suitable for most applications.


Air helper springs from Tough Dog are also available for coil-sprung vehicles, which are also prone to sagging under a heavy load. In the case of this Fortuner, they are fitted inside the spring and are cheaper, since no bracketry is required. A set will cost R4 795. Most vehicles with independent front suspension employ a ‘coil over’ spring design, meaning the shock absorber resides inside the spring. For this reason, it’s not possible to fit air helper springs to this type of front suspension and an upgraded spring is recommended when fitting heavy accessories, such as bull bar or winch.