When it comes to getting a good grip, it is all the suspension components that ensure the most consistent contact with the surface you are driving on. It is also designed to provide consistent and accurate handling for the vehicle, and finally to provide the most comfort possible to occupants. In fact, after creating a viable means of powering the wheels, it was the next most important innovation when the automobile was just getting its footing more than a century ago.
Control arms, Coil Springs, sway bar, leaf springs, bushings, and…OMG!!! It is just too much. Well let’s try and make sense of these terms and see just what these components do.
Early History of Suspension Components
With great thought to price as well as ride comfort most manufacturers used leaf type springs for their suspension. With the release of the Model T in 1908 the world saw one of the first innovations of automobile suspensions from Ford. To save weight and maintain the ride he expected, Ford used only one spring per axle and mounted them transversely. This design became very popular with many manufacturers although it was sometime later before shock absorbers would become important. With the “Runabout” Alanson Brush incorporated the shock absorber with the coil spring, much like a suspension that another man named McPherson is associated with. Alanson had worked with Oldsmobile and Cadillac before leaving to form his own car company in 1904, during this time he tried several different designs of his own and not until his brother wrecked his recently completed “Alanson Crestmobile” did he realize how important the shock absorber was to improved handling for the driver. While Brush motors enjoyed some relative success Alanson’s financial backer had other interests, absorbed by the U.S. Motor company in 1910 the “Runabout” disappeared in 1912 with the collapse of the company.
Straight/Solid Axle Front Suspension Component
There are two primary types of front suspension and several variants of each. The most widely used on early vehicles was a straight axle, typically supported by leaf springs, either one or two, to support the vehicle, cargo, and passenger weight. These were very simple, straight forward suspensions that were rugged but really provided little ride control, even if the customers were not aware of it at the time.
King Pins of The Automotive World
Straight axles use a king pin or a ball joint to attach the spindle and U-bolts to attach the springs, springs were mounted in much the same fashion as today’s leaf spring vehicles, with pivots or slides that allow the spring to work as the overall length of the spring changes while the vehicle travels. Leaf springs are popular even today due to their load carrying ability and the simplicity in which they work. This type of suspension is still used today, particularly on heavy vehicles, you can find solid axle front suspensions on nearly every over the road truck. This is also still a very popular set up for hot rods, using axles set up with a “drop” helps a builder lower his ride with little effort and with the use of either a mono leaf or coil springs and shocks can achieve a decent ride, if spring rate is chosen correctly. The biggest difficulty encountered with straight axle suspensions is not poor ride quality but poor handling. When driving over rough surfaces or imperfections in the road (potholes), the suspension tends to skip as one side reacting to the roughness begins to create a loss of control on the opposite side of the vehicle. Not being able to isolate the action of one front wheel led to the adaptation of independent front suspension.
Independent Front Suspension Components
More complex with more moving components independent suspensions improved the handling experienced by those driving a solid axle car. The most common independent front suspension is one using upper and lower control arms to attach the spindle to the car and a coil spring and shock placed between or above the control arms. While many use coil springs there are numerous variants of the design, short arm/long arm systems have unequal length arms that keep the tire perpendicular to the road even over the harshest of bumps.
Solid Axle Rear Suspension Components
The benefit of solid axle suspension systems is that they are much less expensive. You will find them on lots of large SUVs, vans, and trucks. They can still do a great job of providing the three attributes when combined with good springs and dampeners. Some vehicles like the Ford Mustang famously used a solid axle in the back and an independent suspension in the front until very recently.
Think of the type of suspension as the bones of the system. They do not actually do the work, but they provide the foundation for how the work of achieving all three suspension goals will be completed.
Independent Suspension vs Solid Axle Suspension Components
Independent suspension simply means that the driver side wheel and the passenger side wheel are not directly connected and can move up and down independently. Solid axle suspension is the opposite where both wheels are directly attached to one another with, you guessed it, a solid axle. Independent suspensions have a large advantage in terms of handling, comfort, and added grip in most situations. That is why practically every sports-oriented or luxury vehicle on the market has fully independent suspension.
McPherson Strut Suspension
McPherson style front suspensions use a shock absorber and coil spring combination that attaches to the spindle in place of the upper control arm. This system was revolutionary in helping the designers to engineer lower hood lines and add more room for front wheel drive transaxles without sacrificing ride and handling.
Struts are very similar to shocks in that they serve as a counterbalance to the spring, but the difference is that the struts do more. They are built to support the weight of the vehicle to some degree and often incorporate more parts like integrating the spring as well as mounting points for auxiliary parts like end links.
Suspension Spring Components
Springs are the simplest part of the suspension and they do exactly what you might think they do; they simply allow the wheel to travel without transferring all the force into the chassis of the vehicle. As the vehicle goes over a bump the spring is compressed, but that energy stays in the spring itself and is released much more slowly than it would be otherwise. In part, this dampens the jarring effect to the rest of the vehicle, and in addition, it pushes the tire into the road surface to maintain contact.
Leaf Springs
Leaf springs originally called a laminated or carriage spring, and sometimes referred to as a semi-elliptical spring, elliptical spring, or cart spring, it is one of the oldest forms of vehicle suspension. A leaf spring is one or more narrow, arc-shaped, thin plates (leaves) which are attached to the axle and chassis in a way that allows the leaf spring to flex vertically in response to irregularities in the road surface. Lateral leaf springs are the most used arrangement, running the length of the vehicle and mounted perpendicular to the wheel axle. The more leaves the more support the springs can provide depending on the material density.
Coil Springs
Made of wound metal, coil springs are designed to support the vehicle’s weight. They compress and absorb road impacts, allowing the frame and body of the vehicle to experience minimal disturbances when riding over bumps such as railroad tracks or dips such as potholes.
NUMBER OF COILS – More coils can support more weight, while too many can cause coil bind, a condition where the coils stack solid at or before full suspension compression. This can lead to suspension component damage.
WIRE DIAMETER – The spring rate increases with a higher wire diameter. However, higher grade steel in combination with a smaller wire diameter can handle heavier loads.
Torsion Bar Suspension Components
Another type of spring used in conjunction with a straight axle is a torsion bar, torsion bars absorb the energy through a long rod attached to the axle and the frame, this set up is designed so that the twist in the rod supports the vehicle and the rod then twists during operation to absorb the energy. Torsion bar style suspensions are also used by many manufacturers with the control arm type suspensions. A torsion bar suspension, also known as a torsion spring suspension, is any vehicle suspension that uses a torsion bar as its main weight-bearing spring.
Suspension Bushings
Vehicle suspensions components are in constant movement, unless, of course, you are stopped. Control arms pivot up and down, springs compress and expand, shocks are moving, and all of this must happen in such a way as to provide a better ride, better traction, and better handling. Each of these components must be mounted so they can move freely and still create some isolation between what the suspension is doing and the consumer driving the vehicle. To dampen the activity bushings are used in nearly every pivot point of the suspension. The most popular type of bushings are the standard rubber bushings they have used for years which provide for a great ride and a great deal of insulation from the roughness the vehicle may be traversing through at the time. While there are other types, another popular material for bushings is polyurethane. Polyurethane bushings are not as soft as a rubber bushing so more road feel will be transmitted through to the driver, however, being of a denser material the polyurethane bushings provide for a better handling vehicle and control the changes a vehicle is thrust into easier. Polyurethane bushings, as well as other bushings made of material other than rubber, will typically be found in cars geared more towards performance.
Ball Joints
Among all the various suspension components found on a suspension one of the most critical is the common ball joint. Ball joints provide the connection between the vehicle and the tire/wheel. The wheel mounts on a spindle and the spindle is attached to the control arms with this part. For such a small component, built with a ball and socket design, it takes the absolute blunt force of the vehicle. When choosing replacement parts choose a quality piece that is serviceable with grease fittings. The ball joint allows the suspension to pivot up and down while maintaining proper tire angle and allows the front wheel to turn left or right. This, again, is a very crucial piece of a vehicles front suspension and needs to be inspected, along with the rest of the suspension, for wear or damage regularly, a worn ball joint will lead to, eventually, the spindle coming loose from the control arm creating a loss of control.
Shock Absorber
Shocks are simple devices used to oppose and steady the rebound phase of the spring. Shocks are all about controlling the suspension and its rebound. A spring absorbs energy and releases energy, when going over a bump the spring absorbs the energy and then releases it by pushing back with equal or greater force. Obviously without some sort of damper this cycle will continue, and the vehicle will continue to bounce after hitting a bump, a shock absorber does exactly that, absorbs some of the energy from the spring and controls the release of the energy as well.
They also provide some added resistance to the road surface during hard bumps so that the spring itself is not taking the entire brunt of the force. Shocks are built with fluid inside that is forced through a plunger that has very tiny holes in it. The action of compressing the shock turns that kinetic energy into heat that dissipates from the body of the shock. Without a shock (or a strut), the car would bounce uncontrollably. Sometimes you will notice cars that bounce around unusually after hitting a bump on the road, and those cars have “blown out” shocks that are no longer functioning. Watch for signs of leaking fluid around your shock for a sure bet that it’s time to swap them out.
Sway Bar or Anti-Roll Bar Suspension Components
While we have discussed the main parts of car suspension, there are many auxiliary parts that can improve the overall suspension package of a vehicle. First, every vehicle on the market today uses a sway bar on each axle. The sway bar is typically a single piece of rigid material like steel or aluminum that is designed to transfer energy from one side of the vehicle to the other. This allows the vehicle to reduce body roll from one side to the other as the sway bar directly counteracts that force.
While the springs (leaf, coil, or torsion bar) support the vehicle and the shock absorbers control the energy stored and released by the springs, sway bars, or anti-roll bars control the vehicle. Using either a solid bar or a tube, the sway bar is attached to the frame and pivots inside of bushings while the ends of the bar are attached, with links, to the lower control arm. Going back to our high school geometry we see how the pressure of the vehicle will cause the sway bar to apply equal force, like a torsion bar, to the opposite side of the vehicle. When getting onto an exit ramp and turning right the body will want to lean left. As the body begins to apply its weight the sway bar, or anti-roll bar, transfers energy and raises the right side of the vehicle to maintain control. Different diameter bars are used based on the application, a heavier, thicker bar will be found on a track vehicle where handling is going to be tantamount to winning the race and passenger cars will have a slightly smaller bar to improve handling without sacrificing ride and drive quality.
Sway Bar Bushings and End Links Suspension Components
The sway bar is typically connected at four points on each end with a small part called an end link and, in the middle, twice to the frame with rubber or polyurethane bushings. The end links are then connected to the suspension itself. Now let us dig into those and other bushings throughout the suspension.
Without bushings, none of this would work properly. They provide robust cushioning to keep things from becoming metal on metal or completely loose and pointless. Most all bushings should look about the same when healthy. They are complete, without large gashes and tears. They do not have fluid or grease leaking from them either. When you see those things, it is time to swap them out because a failure of the bushing can cause major problems and will cause quicker failure in other components as they try to take on the additional load.
Ride Height
This is just a basic outline, we are often stuck with whatever suspension system our vehicle has but there are always ways to improve handling, ride and even vehicle stance. Coil springs can be cut to adjust ride height and custom-made springs are available so that you do not have to cut. Leaf springs can be mounted above or under the axle typically to change ride height and leaf springs can be added or removed based on what you expect from your suspension. Leaf springs can also be re-arched or built custom, based on your preference. Torsion bar type suspensions are the easiest to adjust ride height but, like other types of suspensions, the vehicle requires an alignment to ensure proper handling and to control tire wear. The most important thing to consider is the quality of the components you use. Research what you want to do, research the parts, and search related forums online to discover the pitfalls of what you have planned. I also recommend that you keep in mind that anytime you make changes to ride height you also change the geometry of the vehicle and by changing this you are changing how weight is distributed and will affect handling and braking performance, possibly with adverse results. The result you want is a safe vehicle that handles well, rides nicely and maybe, with changes in ride height, has a more aggressive stance.
Finally
As with any suspension component part, always choose the best product to meet your needs. Determine how you plan to drive your vehicle and what you plan to use it for and then purchase quality parts, not necessarily the most expensive, but the highest quality. Most of these components are not difficult to service and replace but it is not easy work either, do not waste your time and your money on a product that does not have a good service life. As what some consider hobbyists we may enjoy working on our cars and trucks but mostly it is for improvement, not to re-do work that has already been done.
