The Science of Suspension – Research & Development

The Science of Suspension – Research & Development

Developing a complete suspension solution for a vehicle is a fairly involved process.

It isn’t as simple as simply making everything a bit longer and a bit beefier, the broad brush style of application simply doesn’t cut the mustard when developing a premium grade solution for the range of different applications people use their vehicles for.

At Tough Dog, we’ve recently taken delivery of the new Nissan Navara NP300 with leaf sprung rear end.  Let’s have a look exactly what goes into every new vehicle suspension we create.

First Impressions

Science of suspensionThe NP300 Navara with the all new five link coil rear axle caused a bit of a splash when it first hit the Australian market. The first 4x4 utility with a coil rear suspension was bound to appeal to off road users. Of course, the leaf spring variant is still a popular variant, which of course meant it was in line to receive the Tough Dog suspension treatment.

“First drive shows the NP300 to be a very compliant ride,” Simon, the head of R&D says. “The Leaf spring being under the axle is the main contributor here, which is different to most utilities that are sprung over the axle housing.”

The first step in any suspension development is to establish the base line of the vehicle, and where the shortcomings in the OEM offering are. While some vehicles have difficulty carrying a heavy load straight out of the factory, others carry the weight without issue, but have difficulty providing a supple ride to the occupants. 

We measure and drive the vehicle at a range of different load points, recording data on the effects of the weight on the spring through key measurement points like loaded camber (the amount of bend in the spring under load) and bump stop gap distances.

From there, the Navara gets pulled apart, and the factory shocks are cycled on our shock dynometer, which measures the resistance force that the shock exerts. The springs get tested for spring rate at their working height. When we compare the figures from the dyno graph and the spring rates with the real world driver’s seat experience, we gain an understanding of what areas need a little TLC to get the most out of the suspension.

First fit out

Load carryingWith our new found knowledge, we create the very first prototypes of the components. “The first set of suspensions is almost never right,” Simon explains. “There will always be a little tweaking based on the real world effects of the workshop changes. What works on paper isn’t always 100% when applied in the field.”

When it comes to the Navara, we found that we needed to place a flat spring perch section into the design to ensure the clamping force of the U-Bolts did not adversely affect the spring’s performance. “We’ve also chosen to make the ride slightly more direct and controlled compared to factory, as the factory ride is very compliant, especially when a load is placed in the vehicle.” Simon tells us.

After all the fine tuning, the loading and unloading and the fitup and removal of the springs has finished, the dust settles and we’re left with a complete set of prototype parts for the vehicle which will need to go into production. “We normally have one more test set of everything made for a final approval,” Simon mentions, “so that we always make sure our quality controls are spot on.”

The result

Suspension testingWhile the product is not released yet, we’ve successfully developed a 40mm lift offering with both our award winning 41mm Foam Cell shocks and also with our 40mm 9 stage adjustable shocks. We’re also going to be offering a 35mm Nitro Gas shock in the rear for light duty users.

On the spring side of the equation, two springs were developed for the front, one to suit vehicles fitted with no accessories and all the way up to a bulbar, and another spring for vehicles fitted with both a bar and a winch.

For a full review of what 4X4 Australia magazine thinks of the Tough Dog NP300 Navara, keep an eye out for the 4x4 of the Year testing later this year.

Tough Dog Suspension’s website has a new feature called Build & Buy Online, which allows you to select the right suspension for your vehicle, and have it delivered to your nearest dealer for collection. You can also arrange to have the dealer fit the suspension if you prefer. To see what complete options Tough Dog have for your vehicle, check it out at

Get the latest info on all things 4X4 Australia by signing up to our newsletter.