Suspension in Your Car: Common Malfunctions and MaintenanceUpdated Jan. 2, 2021
Following our section on the front steering and suspension system, we are going to take a more detailed look at the suspension system itself. A well-tuned suspension system is necessary for a driver to be able to control a vehicle. The main components in the suspension system are the tires, the air in the tires, shock absorbers, springs, struts (in most vehicles), bars, bushings, linkages and joints. Together, these devices manage the relationship between the road and the wheels, and the wheels and the vehicle body.
The suspension system’s primary jobs are:
- Maximizing traction between the tires and the road
- Facilitating stable steering, in conjunction with the steering system
- Evenly distributing the weight of the vehicle across the tires
- Enabling good handling
- Absorbing bumps and dips in the surface of the road, while keeping the body of the vehicle steady
- Canceling out “shock” that would otherwise reverberate through the vehicle, as it travels over uneven surfaces
Most modern vehicles have independent suspension systems, which allow each wheel to move up and down independently of the others. This helps the vehicle maintain good traction across all four wheels when only one wheel passes over a bump or road surface irregularity.
Tires and air
Your car’s tires and the air they contain are essential components of the suspension system. People tend not to think of tires as being involved in suspension, as they have no moving parts. Remember, your tires will compress and reform as they move across the surface of the road. The air pressure within the tire determines to what extent this can happen and thus, how well the tire maintains traction with the road’s surface.
Tires must be inflated to the pressure recommended in your vehicle owner’s manual, not the pressure printed on the tire itself. Improperly inflated tires can damage the vehicle’s suspension and adversely affect traction, as follows:
The tire is more susceptible to overheating, has poorer cornering stability and is less responsive to steering. Underinflated tires can also lead to misalignment or damage to the suspension, as the tire will not be able to absorb impact so effectively.
Traction is worsened as less of the tire’s surface area is in contact with the road. Steering and stability may appear improved, but the ride will be bumpier and more uncomfortable.
Worn tread will also affect tire traction. Both over and underinflated tires can lead to prematurely worn tread. Ideally, you should check your tire pressure every couple of weeks, topping up the air as necessary. When the tread begins to wear down or the tires have reached the end of their lifespan, you will need to replace them with new ones.
The suspension system allows the wheels of the vehicle to move up and down as they travel over bumps, potholes and other roadway irregularities, without the main body of the car being affected. There are several different designs of automotive suspension systems in common use, though they all rely on a type of spring to absorb impact from the road. Most modern suspension systems use coil springs (springs which are shaped like a spiral), which expand and compress as the wheels move over bumps and dips in the road. Springs allow all four wheels of the car to maintain contact with the surface of the road, even when the pavement is uneven.
Spring tension determines how smooth the vehicle rides and how well it maintains traction. Often, the two goals are at odds with each other. Thus, spring tension must be just right, to maximize traction while also absorbing impact from the road. Loose springs usually equate to a very smooth ride, as the wheels can move more in response to bumps in the road. However, the vehicle body tends to move more on loosely sprung suspension. This means that the car will experience more dramatic weight shifts forward or backward, or side-to-side, when braking, accelerating or turning corners. This can lead to loss of traction in one or more of the vehicle’s wheels.
In contrast, tight springs (as often found in sports cars) minimize movement in the body of the car, allowing for better traction when turning and adjusting speed. Of course, the downside to tightly sprung suspension is that it does not absorb impact from an uneven roadway particularly well, resulting in a bumpier ride over rough surfaces. If you notice your car’s suspension becoming bumpier or bouncier over time, it may be that the suspension springs need to be adjusted.
Though springs are very good at absorbing energy, they cannot easily dispel it without moving the body of the vehicle. If the suspension system relied exclusively on springs, the vehicle would bounce every time the springs expand or compress – which somewhat defeats the point of suspension. For this reason, the vehicle’s suspension system features shock absorbers to counteract the movement of the springs.
Shock absorbers connect all four of your vehicle’s wheels to the body of the car. They are either found close to the suspension springs or passing through the spring itself (known as strut suspension). Shock absorbers are essentially cylindrical pressure tubes filled with hydraulic fluid, which is compressed by a piston as the wheel moves upward. This compression forces the hydraulic fluid out through small holes within the piston. As the hydraulic fluid cannot drain into the piston quickly, this process slows the piston down and inhibits movement in the suspension. To put it simply, the unwanted kinetic energy in the springs is absorbed by the shock absorber and turned into thermal energy, which can easily dissipate.
Your vehicle’s suspension system should not require regular maintenance beyond a general check-up, each time you take the car in for a service. Eventually, important component parts such as shock absorbers and springs will wear out and need to be replaced, though they should last for around 50,000 miles.
How rapidly your suspension wears out ultimately depends on how you drive, and where you drive. Driving on level, well-surfaced roads places minimal strain on the suspension and should maximize its lifespan. In contrast, driving predominantly on rural, rough or unpaved roads will increase strain on the suspension, shortening its lifespan.
It is important to pay attention to how your vehicle handles, as problems with shock absorbers will escalate quickly. If you notice wear around the shock absorbers or can feel the car riding less smoothly, get it checked out by a mechanic as soon as possible. Shock absorbers generally fail quite quickly once they have begun to wear. If this happens, the vehicle may not sit level, you may have a hard time maintaining control on corners, and bumpy roads may feel particularly jarring.
Signs that your shock absorbers or springs are starting to fail are:
- Poor handling
- Knocking or banging sounds coming from underneath the vehicle
- Stiffness in the steering
- The ride becomes bouncier (this may be isolated to the front or rear of the car)
If you have any cause to believe there is a problem with your vehicle’s suspension, do not ignore it. Suspension issues can worsen very quickly and are always extremely dangerous. If a spring or shock absorber fails while you are driving the car, it will suddenly become unpredictable and much harder than usual to control. This could easily cause a collision if it takes you by surprise.
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