Explained: New-for-2025 Supercars spring rates

A key technical change is set to arrive for the 2025 Repco Supercars Championship, with teams to get access to two new control spring rates.

As revealed in recent weeks, Pedders and Supercars have worked together to develop two new spring rates for the 2025 season.

Pedders, which has been the Official Gen3 Control Spring supplier to the Repco Supercars Championship since 2023, have devised two new stiffer spring options.

What are springs, and what do we have?

Coil springs are in the suspension of a Supercar, and can be changed with different spring rates to soften or stiffen the suspension.

Spring rate is measured by Newtons per millimetre, which is how many Newtons of force are needed to compress the spring by one millimetre. The higher the number, the stiffer the spring.

Pedders currently supply teams with 17 different variations of coil spring, which vary from 65 to 155N/mm. The current spring rates, measured in N/mm, are 65, 70, 75, 80, 85, 90, 100, 105, 110, 120, 125, 130, 137.5, 145 and 155.

From 2025, teams will also have access to two stiffer options, 168N/mm and 180N/mm.

Why does it matter?

Having a high-performance suspension system is crucial, because the suspension has a significant impact on the car's handling, stability, and overall performance.

All tracks in Supercars are different, and present different challenges. Notably, loads on the car are high around Mount Panorama, while few circuits punish cars quite like the Gold Coast and its brutal kerbs.

Teams constantly work to tune the suspension, which ultimately helps drivers attack circuits more quickly and with greater precision. A good suspenstion set-up can also help maintain stability at high speeds, improve traction, and reduce tyre wear.

These factors are crucial in Supercars, where even the smallest advantage around the track and over the kerbs can make a significant difference in the outcome.

How are springs made?

Currently, teams receive eight of each spring per car, meaning Pedders supply the paddock with a whopping 4800 springs, which equates to 10 kilometres of steel.

A high performance coil spring needs to be manufactured with exacting tolerances, so it has the correct spring rate, and performs consistently and reliably.

Pedders' highly refined manufacturing process sees steel first fed through a furnace set to 980 degrees Celsius, before being fed onto a fully computerised CNC coil winding machine.

They are then drenched in an oil bath before a 30-minute stint inside a gas-fired furnace, where the coils develop their flexibility and elasticity. The ends of the springs are then ground away to remove any impurities, leaving them with a shiny, smooth surface.

Each spring is individually tested to see if it maintains the correct spring rate, before they are powder coated. Powder is attracted to the coil by a magnetic process, where the coil is negatively charged, and the nozzle of the gun is positively charged.

Finally, they're back in the oven to set, for another 30 minutes, before being branded and labelled with technical information.