Tuning suspension for Australian conditions with the new Hyundai Elantra SR
We spent a day with Hyundai’s engineering team as it tuned the new 2017 Hyundai Elantra SR, and discovered that good suspension is science, art and a lot of a teamwork.
What is suspension and how does it work?
Ride is how comfortable the car is as it moves. Handling is how responsive, predictable and even pleasing it is to control input. To some extent the ride and handling are conflicting objectives; we’ve all been in silky-smooth cars that flow over bumps yet are saggily unresponsive to the driver’s inputs.
- Springs – the spring is, literally, a spring, just like what you’d find inside the average Biro pen, but larger. Mostly these springs are metal coils, but they can be rods or even bags of air, commonly now found on buses and other heavy vehicles as well as top-end 4WDs. Springs are there to set the ride height of the vehicle, and absorb the bumps and forces generated when wheels move relative to the body. Hyundai cars, like most modern vehicles, tend to be fairly equally well balanced left and right. This removes the need for ‘handed’ springs, where say the right side of the car is heavier than the left.
- Dampers – you know what happens to a spring when it’s compressed and then released; it bounces up and down and up and down, like a rubber ball dropped on concrete. That’s where the shocks come in, which damp out what would be the resulting oscillation. The dampers work in the same way as a coffee plunger – there’s cylinder of fluid, inside which is a rod connected a disc full of holes. The rod/disc moves up and down inside the cylinder of fluid, damping out the bouncing of the springs, which is why they are more correctly known as dampers so that’s the term we’ll use from now on.
- Swaybars – when a vehicle corners it rolls and transfers weight transfer to the outside of the vehicle. The inside wheels are loaded up, compressing the suspension, and the weight on the outside wheels is reduced, extending the suspension. This rolling is not entirely desirable, so a swaybar is used to control it. A swaybar is a simple metal rod connecting the two wheels on an axle, so the ability of one wheel to move up or down relative to the other is reduced as there’s a limit to how far the swaybar can twist. Because it’s just too simple to have just the one name for any given component swaybars are also known as ARBs, or anti-roll bars.
- Control arms – these are components that connect the wheels to the chassis, all set in complex geometry to allow the wheel to move relative to the car. This movement is not a simple up-and-down motion, as it’s best for the wheel to change angle slightly as it moves to assist with accommodating the changing dynamics from the weight transfer you get when cornering, braking or accelerating.
- Bushes – the dampers and other components are connected to the chassis via mounts typically made of rubber which allow relative movement between the component and the chassis. As the bushes are soft they can also compress and extend, forming part of the impact-absorbing properties of suspension.
- Bumpstops – the suspension’s spring will compress, but only up to a point after which it can’t compress any further and then it doesn’t behave like a spring. When that happens the car needs to absorb the shock by itself. The last chance for the car is the bumpstop, which is typically a little bit of pyramid-shaped rubber that the control arms touch when the spring is fully compressed. If you hit the bumpstops hard you’ll know about it!
- Tyres – even the tyres are part of the suspension, as they are filled with air which is compressible, and that means they can absorb impacts as well as rebound like a spring. The grip of the tyre has an effect on how much weight shift there will be around a corner; high-grip tyres mean higher cornering speeds and more weight transfer and thus suspension compression.
What needs to be tuned?
The car and the test routes
The team and the work
An intensive development cycle
The challenges…and solutions
The biggest challenges the team face are the conflicting requirements of suspension – for example, balancing an idealised handling model against ride comfort, and both against noise. Then there’s the volume of work to be done, because it’s not just one tune for every variant of a car. Diesel engines are heavier than petrol engines, so they need a different tune and it’s not just a case of stiffer springs in the front as changes to the front affect the rear too. Then there’s all-wheel-drive (AWD) and two-wheel-drive, or in the case of Hyundais, front-wheel-drive. That’s a challenge for a couple of reasons – first the AWDs models weigh a bit more, but they also handle slightly differently. That’s due to the weight difference and the extra set of driven wheels, but also differences in the way suspension reacts depending whether the wheel is driven or not driven.
The final signoff
- Santa Fe offroad test
- i30 long term test
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- How stability control and traction control work