How Does a Car's Steering Work?
Ellie Dyer-Brown, 6 months ago
5 min read
- Steering
- How it works
FixMyCar explains how steering systems work and how they have evolved to make our lives easier.
Did you know that turning a car used to be considerably harder than it is today? The development of power steering in the 1920s was nothing short of revolutionary. It allowed any driver to control any vehicle - including the biggest 4x4s - with minimal effort, something many of us take for granted.
So, what exactly is power steering, how does it work, and how does it differ from earlier steering systems? Read on to find out.
Contents
Rack and pinion steering components
The evolution of power steering
What to do if your power steering light comes on
In a nutshell: Modern cars often use rack-and-pinion power-assisted steering. This system makes it easier to turn the steering wheel and converts the movement of the wheel into the linear motion needed to turn the wheels.
How mechanical steering works
Most cars on the road today use a rack and pinion steering system. The steering pinion is a circular gear that locks teeth on a linear gear (the rack), converting the rotational motion of the steering wheel into the linear motion that turns the wheels left or right. Although the rack is separate from the front axle, it connects both wheels to turn at the same angle when the steering wheel is used.
Turning the steering wheel in a purely mechanical system is more difficult than you might think, which is where power steering comes in.
Rack and pinion steering components
Rack
The rack is a solid metal component that connects the wheels to a series of U-joints, which move the rack pinion to the left and right as the steering wheel turns.
Pinion
The pinion is a small gear attached to the steering rod. It meshes into the rack’s teeth as it moves.
Steering column
The steering column encloses the connections to a car’s steering gear, carrying the steering inputs to the rack.
Tie rods
Tie rods are found on each front wheel. They connect the steering rack to the steering knuckle and ensure your car travels straight when the steering wheel is centred. The length of the tie rods can be adjusted to ensure correct alignment and optimised steering.
Steering knuckles
Steering knuckles are chunky pieces of metal with several protruding arms behind the wheels. They connect the wheel hub to the suspension via ball joints. Each steering knuckle has a lateral arm attached to a tie rod, which either pushes or pulls the arm, depending on the direction of the steering wheel.
How does power steering work?
Power steering is a system that reduces the effort needed for a driver to turn the steering wheel. It does this by using another power source to assist the steering so that there is less resistance when turning the wheel. It also makes a car’s ride smoother by absorbing shocks from the road.
There are two main types of power steering: hydraulic and electric. They do the same job in different ways.
Hydraulic power steering
Hydraulic power steering was popular from the 1950s to the early 2000s. It uses hydraulic fluid pressurised by a pump powered by the engine, which amplifies the force when you turn the wheel.
However, this type of power steering has downsides, the most significant of which is that it wastes energy because the pump runs at all times, even when driving straight. The hydraulic fluid also needs replacing at regular intervals.
Electric power steering
In electric power steering (EPS) systems, an electric motor sits between the steering wheel and pinion and amplifies the movement of the steering wheel through a series of planetary gears.
Sensors provide the ECU with information about how much the driver turns the steering wheel. It then adjusts how much the electric motor amplifies the motion based on things like the car’s speed. At higher speeds, the system makes the movements less pronounced.
The planetary gears make it much easier to turn the wheel and allow the rotation to be strengthened by the electric motor, which can turn the pinion with much less effort. Electric power steering is the most common type in modern cars.
Benefits of EPS
EPS has many benefits, such as:
Improved fuel economy compared to hydraulic systems.
No need for regular maintenance.
It is used for several other convenience features, including automatic parking and lane changes.
Electrohydraulic steering
Electrohydraulic steering is a hybrid system that functions like hydraulic power steering but uses an electric motor to power the pump instead of the engine. It wastes less energy than a fully hydraulic system but doesn’t enable all the features that EPS is used for.
Electrohydraulic systems are pretty rare and mainly used in heavy-duty pickup trucks.
The evolution of power steering
Car steering was originally entirely mechanical, which meant it required a lot of effort to turn the steering wheel. In larger vehicles, the wheel would often be comically big like it belonged on a sailing boat, and you would have to turn it many times to manoeuvre or park.
Power steering changed all that by requiring much less strength and effort from the driver to turn the wheel. It also allowed engineers to improve steering response (how quickly the car turns when you turn the wheel). The first system on a production car debuted in the 1951 Chrysler Imperial and quickly caught on.
By adjusting the steering ratio (how much you have to turn the wheel relative to how much the front wheel angle changes), it became much easier to steer cars - almost effortless.
In the 2000s, a new chapter in the history of power steering began with the evolution from hydraulic to electric power steering. This transition not only offered additional benefits but also reduced the maintenance demands, making it a more user-friendly option for car owners.
What to do if your power steering light comes on
The power steering warning light shows a steering wheel with an exclamation mark beside it. Find a safe place to stop and investigate if it appears on your dashboard.
In vehicles with hydraulic power steering, the first thing to check is the system’s fluid level. If it’s low, top it up using the correct fluid (you can find this information in your owner’s manual), and see if you can spot any leaks.
With an EPS system, the first port of call should be to try switching it off and on again. Failing that, open the bonnet and check the battery’s connections are attached and undamaged.
If you’ve performed these checks but the problem persists, have your car checked by a mechanic to find out what has triggered the warning light. It might be an electrical issue or something more serious. Either way, you should never take chances with your steering.
Common power steering problems
1. Low or leaking power steering fluid
Power steering fluid is typically red, pink or amber. It creates a hydraulic link between the wheels and steering wheel, making it easier to turn, and also acts as a lubricant. Signs of low fluid include:
Difficulty turning the steering wheel
You can top up the fluid yourself, but the same thing will happen again if there's a leak. That’s why it’s worth having the system checked by a mechanic.
2. Loose, worn or slipped belt
If you’ve noticed a screeching sound or any other unusual, high-pitched noise, it could be due to a problem with a belt in the steering system. A mechanic may be able to tighten the belt for you, which is a relatively inexpensive fix. If it’s damaged, it will need replacing.
3. Cracked hose
Rubber hoses that transport power steering fluid around the system wear out over time and may develop cracks, leading to fluid leaks. Look for puddles of red or pink fluid under your car. Even if you can’t spot any, repeatedly having to top up the reservoir indicates that there is a fluid leak somewhere.
4. Slipped hose coupling
The coupling connecting the hose to the rest of the system can work itself loose, allowing fluid to leak. This issue is easy for a mechanic to fix.
5. Damaged pump
Hydraulic power steering systems use a pump to transport fluid. While it is a reasonably durable component, it will wear out eventually. If you’ve noticed your steering is more noisy than usual, it could be due to a problem with the pump.
How to fix power steering
Problem: unresponsive electric steering
Use a code reader to find the fault code. If you don't have one, check your fuse box and look for wiring or battery issues. Switching your car off and on again may reset the electrical components, providing a quick and temporary solution. However, you should have your vehicle checked by an auto electrician to find the source of the problem if it isn’t immediately apparent.
Problem: loss of hydraulic power
When your steering wheel becomes very difficult to turn compared to normal, it’s often due to loss of hydraulic power. Check the power steering fluid reservoir; if it’s low, top it up. Doing so will provide a temporary fix, but you’ll still need to have the system inspected for leaks.
Problem: grinding, whining or squealing noises
The hydraulic pump (pictured below) is most likely to blame. If you feel comfortable going under the bonnet, you could inspect it yourself. But if you lack mechanical knowledge, the best thing to do is take it to a garage or call a mobile mechanic.
Problem: power steering fluid leak
Leaking fluid compromises the safety and reliability of your car. Contact a mechanic as soon as possible to arrange a leak repair.
Are you experiencing issues with your car's steering? FixMyCar can help you find a reliable local garage for a repair.
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Written by Ellie
Ellie is FixMyCar's Content Writer. She has over three years of experience writing about cars and regularly collaborates with automotive experts to provide trustworthy advice for drivers in a language they understand. Her work has been featured in Yahoo! Finance, iNews, The Daily Express and The Sun. She has a BA in English literature and an MA in creative writing from Durham University. Outside of work, Ellie follows F1 and eagerly awaits Ferrari's next era of dominance in the sport. She drives a Suzuki Swift.