One of the most complex subjects in tuning, suspension is a vital part of any car from stanced show stoppers to time attack monsters, luckily we’re here to tell you all about it…
What is suspension and why do we need it?
Your suspension makes up a huge amount of the parts underneath the body, in fact, every single part that somehow connects your wheels to your car counts as suspension; and that’s a hell of a lot of parts. Without suspension, aside from having nothing to bolt your car’s wheels to, there would be no way for your wheels to move independently of the chassis, but why we need that to happen is a little more complex.
First up, you could remove a car’s shocks and springs and replace them with a solid bar, meaning no movement at all, but the car would not only become about the most uncomfortable thing ever to drive normally, but it would actually handle like absolute crap even on the flattest surface. While low and stiff is considered good for handling, even the stiffest suspension moves far more than you might think, and trust us, some people have tried running solid suspension on cars, even in F1; and it really never works.
You might think “well go-karts have no suspension, and they handle awesomely”, but even that’s not actually true. Go-kart chassis’ are designed to have a lot of flex in them, so the chassis itself works as the suspension; a rock solid go-kart would handle just as crap as a car with solid bars instead of shocks and springs. Even the lightest cars weigh hugely more than the heaviest go-karts, so even if you designed a car to use the chassis as suspension like a Kart, for a car chassis to have enough flex in it to work as suspension, it would be so floppy the car would be totally undrivable; basically, for a car to handle, you NEED correctly working suspension.
From a comfort point of view, the need for suspension is much more obvious, but thinking the softer the better isn’t true here either. If it’s too soft it’d be so wallowy it would make the car bob and rock over even the smallest bump or tiniest throttle, brake, or steering movement, so you’d probably feel sick by the time you got to the end of your street!
It’s a subject that covers far more than just the shocks and springs most of us imagine, in fact, they’re just a fraction of the parts involved. For Suspension Part 1 though, we’re dealing with static suspension and that’s purely because the vast majority of cars come with that as standard. We’ll get on to more specialist active suspension, like hydraulics and airbags later, but for now it’s worth knowing that however you choose to modify your suspension, this will be the stuff you’ll be tweaking or taking out. Here’s what’s what…
These are the main suspension component that stops your car’s chassis from just sitting on top of the wheels. Aside from doing that, they have two other main jobs; to cushion the car over bumps or pot holes, and to help the wheels keep in contact with the ground when one or more wheels hits a rough spot. How they do both jobs is simply by doing what a spring does best – compressing or expanding, allowing the wheel that hits the bump or dip to move up and down in the wheel arch, while (ideally) leaving the body and the rest of the wheels moving along as smoothly as possible.
The two main variables with springs (aside from being the correct diameter to fit your car,) is length, and stiffness – often known as spring rate. You don’t need us to tell you that a shorter spring will lower your car, but go too low (unless you got shortened shocks too), and you’ll end up bottoming out the shocks, which is really bad for handling. Spring rate is the main (but not only) factor in how hard your suspension is. Springs for specific applications tend to be already rated at a suitable stiffness for that car, but they’re not always to everyone’s tastes, and depending what you’re using the car for, stiffer or softer ones may be needed.
These are also known as dampers, and this name gives a big hint to what they’re there for. The job of a shock absorber is to control the movement of the spring. Without a shock, the spring would just keep moving, making for a bouncy and uncontrollable ride which is no good for performance or comfort.
Shock absorbers come in two main forms, either with the coil spring mounted on top (or totally separate to the shock), or as coilovers, where the spring literally sits around the shock. While the main reason for the invention of coilovers was to create a more compact and lightweight design, for most of us, the main plus point of coilovers is that the spring seat is threaded to the body, allowing it to be easily moved up and down, adjusting the ride height of the car.
While most standard and budget aftermarket shocks aren’t adjustable, higher-end setups are adjustable for stiffness (more on this later), and full-on race-spec items are not only multi-way adjustable but also feature trick additions, such as remote reservoirs to further improve their performance.
These tend to be found on the back of French hatchbacks, though they’re fitted to other cars too. Torsion ‘springs’ would actually be a better description of what they do, which is effectively replace the job of coil springs. They work in a similar way to a go-kart chassis – the vertical movement of the wheels acts against the torsion bar, which although it’s made of solid metal, is able to twist slightly, allowing the wheels to move up and down when needed.
Just like the springs they replace, thicker and stiffer torsion bars are available for many popular performance cars, and while they’re not as straight forward to replace as springs, they can be uprated in just the same way.
These are the hinged arms that not only mount your wheel hubs to your subframe/chassis, but also control the arcs of movement as the wheel moves in the arch, which are key to your car’s handling abilities. As already mentioned, wheels move up and down in the arch as allowed by the spring and shock absorber combo, but on most suspension designs they don’t just move up and down. They can in fact move in all directions depending on the type of movement the car is doing at the time.
Standard control arms are designed with the intention to put the wheels at an optimum angle for the handling characteristics the factory required, but when ride heights or the use of the car is changed from standard, the control arm settings may become far from optimal. This is why adjustable control arms, which allow front and rear camber, toe, castor, and even wheel track width adjustment, are so popular on tuned road and track cars.
ARBs are another form of torsion bar, but these are fitted to the front and rear of almost all cars these days. Their job is to supplement the conventional suspension springs rather than replace them.Asyoumighthaveguessed,ARBsexisttohelpresistbodyroll– ifyousimply made the shocks and springs stiff enough to eliminate body roll on their own the suspension would be too hard to work properly on the vast majority of surfaces.
Thicker and stiffer ARBs are a common aftermarket upgrade, and some high-end versions are actually adjustable; in fact, some race cars have in-car adjustable ARBs, enabling the driver to adjust roll stiffness while out on track! ARB settings are a good way to change the handling characteristics of the car too, with a stiffer rear bar tending to increase oversteer, and a stiffer front bar tending to increase understeer.