The Science of Suspension – Choosing the Right Gear

Aftermarket accessories can easily affect factory suspension. We documented a fitout on our 2016 Toyota Hilux, to show just how easy this is achieved.

The Science of Suspension – Choosing the Right Gear

Vehicle manufacturers have a lot of people to please if they’re going to make a vehicle that really satisfies the market. 

While the end result is often a great motor car, there will always be a few short comings in a vehicle when we start to focus on a specific application. With the abundance of accessories available today, when things start being fitted to your vehicle, the weaker points of the factory suspension start to show through. To show just how much the weight of a bull bar and winch can affect the vehicle, we documented a fitout from start to finish on our 2016 Toyota Hilux.

Tough -dog -hilux -stillIn the beginning…
The 2016 Toyota Hilux SR5 that rolled off the production line and into our fleet was an SR5 dual cab spec, and the handling from factory was… in a word, jarring. Toyota had designed the vehicle to carry a load well (it is a commercial vehicle after all) and carry a load it did.

The trade-off was a jarring ride when the vehicle was empty. Our R&D department went to work, and we developed the 40mm Lift kit options that you can see at The ride quality was vastly improved, and all was right in the world.

Tough -dog -hilux -uphill -drivingBring on the accessories
We then fitted out our Hilux with a Steel Bull bar and a 9000lbs winch sporting steel cable. The weight over the front was increased, and the front coil spring originally fitted, and designed for accessory levels up to a bull bar but not with a winch, was no longer able to handle the weight. 

Apart from the drop in height as a result of the extra weight, the handling and ride comfort of the vehicle took a small backward step as well. The weight of the vehicle had been increased, and naturally that meant that the turn in characteristics were not as nimble as in factory trim. The vehicle, as expected, felt very nose heavy. The other side effect was that because the weight balance had been pushed forward, which pulled weight off the rear axle, and had the effect of stiffening the rear end of the vehicle.

The front and rear of any vehicle cannot be taken in isolation, the vehicle works as a whole platform, which is why things that happened over the front axle caused side effects through the whole suspension system. It was time to fit our heavier ‘bar and winch’ spring, to counter the effects that the increased weight had on the Toyota.

Tough -dog -hilux -drivingRim to Guard measurements

Vehicle on Original 18” Wheels

Measurement Key

Original Vehicle

With 40mm Lift

Add Bar & Winch

Bar & Winch
(With New Springs)

P/S Front

D/S Front









P/S Rear

D/S Rear









Note: Factory vehicles can vary by up to 10mm in ride height.

The weight of just two of the most common accessories on the vehicle cause the vehicle height to change dramatically, losing 20mm as a result of the fitment. Changing the front spring shifted the weight back onto the rear axle, and corrected both ride height and handling characteristics. We’ve noticed though that some of the newer bars coming onto the market are heavier than previous bull bar styles. 

Before -and -afterIt is for this very reason that the Tough Dog suspension offers spring choices specifically to suit the accessories fitted, to ensure ride height and quality are not compromised in your specific application.

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



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