Underneath the body of a car, there are three fundamental areas of importance. The chassis (which everything is bolted to), the powertrain (engine, gearbox, differential and driveshaft) and the suspension.
On the face of it, both road and race car suspension systems appear to be very similar in terms of what they do and what the systems consist of. However, there are some subtle differences which have a large impact on how race suspension performs.
What’s the difference between road and race suspension?
The suspension on a road car is designed primarily to support the body of the car, but also to provide a comfortable ride for the occupants. This means that the components used by the vehicle manufacturer tend to be softer in a bid to better cope with the road conditions for everyday driving.
In contrast, suspension for a race car is all about maximising performance, often resulting in a much stiffer ride.
The other main difference is that on a standard road car the suspension is fixed at a certain level, both damping on the shock absorbers and the anti-roll bar stiffness. But on racing suspension, there is often a greater flexibility in the amount of adjustment available which is due to the necessity of making the car suit the particular track or stage surface to better optimise performance.
What does race suspension do?
The suspension on a competition car has the same basic function as a road car, which is to support the body of the vehicle. However, the requirements which are placed on race suspension systems and the individual components escalate much higher than that.
In essence, race suspension has two main roles. The first is to control the weight transfer of the car both laterally and longitudinally to improve cornering ability, while the second is to control the impacts from bumps or kerbs to maintain constant contact between the tyre and the road surface.
The end result of optimising both of these elements is an increase in grip which, ultimately, leads to better lap or stage times.
Unfortunately, finding the best performance is not just a case of a one size fits all, fit and forget racing suspension kit. There are various components that make up the suspension system on a car, and each of these have their own variables in terms of adjustment and stiffness.
The key to unlocking all this potential performance is to find the optimal combination of settings and components that best suits both the car and track conditions on the day.
How do I adjust the suspension?
The main items to look at changing are the dampers and springs. This is where you will find the largest amount of available adjustment as well as the greatest potential for performance improvements in terms of the way the car drives and your lap times.
There are a couple of routes that you can go down when looking to upgrade these items, the first of which is to go for a vehicle specific suspension kit, also known as a coilover kit. These include both the dampers and springs with the specific fixings to suit your make and model of car. This is a great solution if you are converting a standard road car into a competition car as you can utilise the existing suspension mounting points and unlock various adjustment options to tune your suspension including ride height, bump and rebound. We’ll focus more on what this does and why it is important later on.
The other option is to fit a motorsport-specific damper and combine it with a set of race springs. This option requires a little more forward planning and calculation to get right because there are several different configurations available in both the damper and the spring.
Rather than the damper being supplied in the correct dimensions to directly replace an OE specification unit, there are various options to choose from including the body diameter, open-closed length as well as the mounting type.
These dampers don’t use the standard vehicle damper mounting points, either, and instead use a spherical bearing or polybush-style fitting. This means there may be some alterations required in the mounting points on your car. The universal nature of these dampers makes them ideal for use in bespoke car builds or replacing dampers on purpose-built race cars such as prototypes.
Both the body diameter and the open-closed length options are directly related to the type of spring that you use. Unlike the springs on a road car, race springs feature a linear diameter and are available in individual spring rates meaning that you will need to figure out what spring rate is best for your car. This can be a complicated process involving corner weights and suspension geometry but obtaining the correct spring rates is an important part of getting the most out of your car. (If you are unsure of where to start, have a chat with our technical sales team who will be able to provide you with some useful pointers to help make the process easier).
Away from the springs and dampers, other suspension components that can be changed and upgraded include the anti-roll bars, bushes, and top mounts as well as adding a strut brace.
How does it improve the handling?
So, there are many different parts of your car that you can look to change in a bid to improve the handling, but what benefits can you actually get from upgrading these components?
As mentioned earlier, you can change the ride height, bump and rebound with a set of motorsport dampers. In terms of the effect these changes can have on your car, reducing the ride height lowers the centre of gravity meaning that the effect of the weight transfer as the car transitions between corners, accelerating and braking is reduced.
The bump and rebound refer to changes to do with the stiffness of the damper and how it reacts to damper movements. The bump adjustment relates to how quickly the damper can be compressed, while rebound relates to how quickly the damper returns to the original position.
Having a high value for both bump and rebound will result in a very stiff damper which can cause the car to be very nervous and twitchy over bumps or kerbs due to not having any compliance to sudden impacts.
A soft damper setting will ensure that the car is not unsettled by bumps as much, but it will mean that the car is less responsive in the corners due to more of the weight being transferred but at a slower rate.
It is worth remembering that both bump and rebound can be tuned independently on most competition dampers. This means that you can have softer bump setting to help absorb the impacts from kerbs but run a stiffer rebound that allows the damper to return to its regular position much more quickly, allowing the tyre to maintain a more consistent contact with the road surface.
The optimum setting very much depends on the car and is often a compromise. However, once you have found the best setting for a given track or weather condition, it is not likely to work as well at a different track. So, you are always having to tune the suspension setup to get the most out of the car.
Anti-roll bars and braces
The anti-roll bars, also known as sway bars or ARB, have the job of reducing the body roll of the car. This helps to control the balance by reducing the amount of lateral weight transfer through the corners by using thicker tubing to increase rigidity.
Some anti-roll bars feature an element of adjustability by changing the length of the lever arms which can further improve the stiffness and adds another element of tuning capabilities in the search for the ideal chassis setup.
A strut brace is another good addition to help improve the handling of the car. These bars are mostly designed to attach to the top mounts of the front shock absorbers, but there are some applications which feature a lower strut brace for additional strengthening.
Having one of these braces installed reduces chassis flex and helps to maintain a greater consistency in the suspension geometry, making for a more consistent driving feel.
Not only do polyurethane bushes offer a greater strength over rubber bushes, they can also help to improve the responsiveness of the car.
Over time, standard rubber bushes start to deteriorate, causing some play and affecting the suspension geometry, resulting in poor car handling, braking instability and even (to some extent) increased tyre wear. As polyurethane bushes have a much-improved resistance to wear, they can retain their strength for longer periods of time, providing better handling for longer.
The suspension system on a car is not only a vital component, it also holds a lot of potential for improving performance. But upgrading your suspension for motorsport use can be as simple or as complex as you want it to be.
If you have any questions about what we have spoken about in this article, our technical sales team are on hand to assist you in finding the right suspension upgrade for you. You can either give them a call on 01978 664466 or send them an email on firstname.lastname@example.org.