Exclusive: New Aussie-developed suspension aims to deliver best of both ute worlds 

A new Australian-developed rear suspension system is promising to fix ride and handling shortfalls found in utes when carrying heavy loads... without comprising lightly laden driving behaviour.

The catchily titled HRDAS (or Hybrid Relaxation Damping Air Suspension) is the work of the former Ford Australia chief chassis engineer Alex de Vlugt.

Essentially, it’s a development of the aftermarket air spring (or airbag) suspension systems used to bolster standard ute rear-end setups, adding two remote air reservoirs linking the airbags with air resistance (stiffness) and ride height controlled by a valve. 

“In unladen condition the system ‘pretends’ to not be there,” de Vlugt said. “It has negligible effect on ride, handling and steering.

“In laden condition, the system is designed to replicate the unladen ride behaviour as much as possible.

“Also, in laden condition the system is designed to create more understeer to counteract the inevitable increase of oversteer resulting from the added loads over the rear axle and shift in centre of gravity.

“And on top of that it generates extra body damping with added load to prevent too much float.”

HRDAS is a direct response to the chassis tunes of utes such as the big selling dual-cab Ford Ranger and Toyota HiLux that are focussed on light-load ride and handling comfort.

As a result, they can struggle to cope with the heavy-duty payload and braked towing requirements their makers claim they’re designed for. 

At carsales, we’ve repeatedly reported on these shortfalls in various reviews and comparison tests.

A key issue this tune creates is the loss of ground clearance and suspension travel as the rear-end sinks under the weight of a load, be it in the tray, a caravan, or both, exacerbating fore-aft pitch. 

Conventional air springs are a widely offered solution to this, but also permanently increase the suspension stiffness, affecting both ride and handling negatively. If used incorrectly, such as the owner overloading the vehicle, airbags can also contribute to frame breakages.

“Ex-factory, utes … are tuning-wise walking a tight-rope to offer an acceptable ride unladen, while still being able to cope with the heavy payload and braked towing requirements,” de Vlugt said.

“When solely relying on conventional spring and damper elements, this creates a compromise in which the unladen ride can best be described as ‘firm’ or ‘choppy’, while under load the suspension sags, the vehicle becomes floaty, lacks ground clearance and may even start to feel less sure-footed.

“By adding a typical aftermarket airbag system, the sag issue can very effectively be resolved, but this solution brings its own issues: both in unladen and laden condition there is an added spring stiffness generated that has negative consequences for ride and handling.”

While primarily focussed on pitching HRDAS to automotive brands as a factory fitment, de Vlugt said it could also be employed in the aftermarket as a cost-effective improvement over Gross Vehicle Mass (GVM) upgrades currently on offer.

“To be honest, none of these GVM upgrade kits come across as particularly thoroughly fine-tuned.

“Certainly not to the degree that the OEMs tend to do. You often lose a lot of ride performance, particularly unladen ride, but even fully laden they’re sometimes not very flash.”

De Vlugt said his practical and CAE (computer aided engineering) testing has shown HRDAS retains standard ride height and good ride and handling balance on- and off-road whether lightly or heavily laden.

A patent is pending for HRDAS in Australia and applied for internationally.

The system can work with any ute, be it leaf spring or coil spring, body on frame or monocoque. It is also adaptable to SUVs, passenger cars and light commercial vehicles.

The Australian-based Dutchman is best known in Aussie automotive circles for leading the dynamics development of the BA Ford Falcon, which adapted the Control Blade independent rear suspension to a rear-wheel drive car for the first time. 

De Vlugt also oversaw chassis development of the Territory SUV and FG Falcon, plus his team tuned the chassis of the final FG X Falcon Sprint.

His Ford career also spanned stints in Germany and the US before ultimately leaving the blue oval in 2019. He now runs his own consultancy, AdV Automotive Engineering. 

De Vlugt’s journey with HRDAS began when he bought a first-generation Ranger Raptor and wanted to uprate its 700kg payload.

He installed aftermarket air springs but found they restricted wheel travel, were hard to fit and rattled loose off-road.

“The worst thing is it completely destroyed the character of the Raptor,” he said. “It became very hoppy from the rear end ... too oversteery, so I became very good at building them in and out because every time when I was not towing a caravan, I took them out.”

De Vlugt developed HRDAS from there and has now tested it with up to 1200kg in the Raptor’s cargo box. 

“It’s perfectly fine,” he said. “It drives really very well with that.”

De Vlugt is in negotiation with at least two ute manufacturers about using HRDAS as original equipment and said it could also become an aftermarket option, describing the system as “low cost” – although he didn’t quantify what that meant. 

For reference, airbag kits typically retail for around $1000.

“I believe that it’s really very suitable to be an OEM (factory) installation, because it enables the OEM to find your perfect suspension tune in an unladen condition,” de Vlugt said. “And then science will take care of the rest.

“So you don’t need to spend a lot of time re-tuning or making trade-offs at higher payloads, all that stuff. 

“I think there’s a real opportunity for OEM to create added value by creating higher payloads without compromising your unladen tune.”

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