How Your Car's Steering Works
No matter how complex and smart your vehicle is, without a driver it is a piece of metal packed with modern electronic devices and systems. All of them are operated by a driver, who uses dashboard controls and the steering system to keep the vehicle moving. The latter is the main and most crucial way of communication with your vehicle, allowing you to direct the vehicle where you need.
Even if vehicles lose a steering wheel one day, they will still be equipped with a steering system. Since the invention of the first vehicle, a steering system has dramatically evolved from a manually operated steering system to modern hydraulic-operated and computer-controlled electrical steering systems, which provide a driver with the steering assist, and some of them can even drive a vehicle without involving a driver.
Regardless of the type of your steering system, it does the same job, converting rotational force of your steering wheel into swiveling movements of the front wheels. Back to basics, the simplest steering system consists of a shaft connected to the front wheels with tie rods and another shaft connected to the steering wheel and the first shaft. When you turn the steering wheel, its shaft causes the first shaft to move the front wheels. In a typical vehicle, the job of the steering shaft is performed by a steering column that is attached to a steering gear. The latter moves a pitman arm, which in turn, moves the drag link and tie rods connected to the front wheels.
When you drive, your wheels move up and down without sacrificing your steering. This happens thanks to spindles attached to the wheels as well as universal joints and ball joints that connect the steering column to the gearbox, and the latter to the spindles. Such suspension and steering systems arrangement allows your steering linkage to go up and down, while still providing proper control over your front wheels.
While all steering systems serve the same purpose, they can do their job in a different way. Let’s take a look at the most common steering system designs.
Rack-and-pinion steering systems
This is the most common type of steering system found in most cars and trucks on the road. This simple yet very durable and effective design features a rack with teeth on one side and a steering shaft with a pinion gear on its lower side. The steering shaft transfers the rotation of the steering wheel to the rack which then moves the wheels left or right thanks to tie rods on its ends attached to the spindles. Each tie rod on its straight end is screwed directly into the rack, while its other end is angled and goes into the spindle, allowing the wheel to move in different directions.
The force that a driver needs to apply to the steering wheel to turn the wheels depends on the size of the pinion gear. The larger the gear is and the more teeth it has, the more force you’ll have to apply to turn the vehicle. By contrast, a smaller pinion gear with just several teeth will make it easier to spin the steering wheel. At the same time, the vehicle will be turning slowly. Depending on the weight of the vehicle and its size, its engineers calculate the optimum pinion gear size to provide both adequate steering wheel response and ease of operation. On larger vehicles, such as trucks or SUVs, power steering is often used to assist the driver.
Rack-and-pinion power steering systems
Just about all modern vehicles today come equipped with power steering. The most popular design is power-assisted rack-and-pinion steering. It is similar to the standard rack-and-pinion design, however, also features a cylinder with a piston, which is attached to the rack. The system also comes with a power steering pump which supplies pressurized hydraulic fluid to the piston and cylinder assembly.
The other essential component of the rack-and-pinion power steering system is a rotary valve, which supplies more pressure to one of the sides of the piston that corresponds to the side you turn the steering wheel. When your vehicle is moving straight forward, the rotary valve sends the same amount of pressure to both sides of the piston. More advanced systems provide control over the steering, monitoring the speed of the vehicle, its load and several other parameters to give the driver just the right amount of power assistance he or she needs. They provide more power support at low speeds and reduce its amount when cruising to avoid oversteering.
Electric power steering systems
It is the most advanced type of steering system available today. Instead of hydraulic pressure and a linkage, they rely on an electrical motor attached to the steering shaft or the rack-and-pinion assembly. The motor is operated by the control module, which monitors the position of the steering wheel with the help of sensors to provide steering support when the driver needs it. It also analyzes the vehicle’s speed, its load, and other factors to provide just the required amount of steering support.
Unlike traditional hydraulic-operated power steering systems, which constantly draws some engine power to operate, electric power steering systems are fed by the electrical system of a vehicle, so they do not compromise on the engine performance. In addition, they can be adjusted on the go, which makes them extremely efficient, delivering the best driving experience possible.
Recirculating-ball steering systems
A recirculating-ball steering system is an alternative steering system design that can be found on older vehicles and large trucks. It also comes with a steering column, but instead of a rack-and-pinion assembly it utilizes a worm gear that features a spiral that runs its length. This worm gear moves inside a metal block that has gear teeth on one of its sides. Another essential component of this steering system is a sector gear that is attached to the pitman arm. The latter moves the steering linkage attached to the wheels.
This steering system design utilizes a complex linkage, which consists of inner and outer tie rods, a drag link and an idler arm. All of them work together to turn your front wheels left or right depending on the position of your steering wheel.
To reduce the friction between the metal block and threads that run inside of it, all recirculating-ball steering systems come with ball bearings. This is actually why a recirculating-ball steering system has this name
Just like rack-and-pinion steering systems, their recirculating-ball counterparts can also come with power support. It is based on the same principles as the power steering support of rack-and-pinion systems. Power recirculating-ball steering systems also rely on hydraulic fluid pressure that is applied to a specific side of the block to help the driver turn the wheels.
Regardless of your vehicle’s year, make and model or its body type, geometry is a key to smooth and safe ride. This is also true to proper wheel alignment which allows for preventing the vehicle from pulling to one side, and is crucial for comfortable steering and normal tire wear. Your wheels must be properly aligned in three directions, known as toe, camber and caster. Let’s describe them one by one.
Toe is the most important alignment angle. This type of adjustment is performed on every vehicle no matter whether it is a two-wheel drive or four-wheel drive one. Toe sets how your wheels angled towards each other. Improper toe adjustment can lead to uneven tire wear, wandering driving, squealing noises, and an out-off-center steering wheel.
Another crucial wheel alignment angle is called camber. It sets the tilt of the top of the wheel against the vertical line that goes through the center of the bottom of the wheel. Depending on the wheel angle, it can be positive (outward tilt) and negative (inward tilt). Usually caused by bad ball joints, worn-out bearings or bent spindles, improper camber will also shorten the service life of your tires.
The third alignment angle cannot be adjusted or changed. It is set by the manufacturer when assembling the vehicle. Caster stands for the angle of your steering axis when you look at the vehicle from the side. As a rule, most vehicles come with a positive caster, which improves handling and driving stability. The caster of your vehicle remains the same throughout its service life, however, it can be affected due to an accident or faulty suspension components.
Steering system maintenance
Most steering systems are easy to maintain and do not require regular inspection unless the other is mentioned in your owner’s manual. If you have a hydraulic-powered steering system, the fluid level must be checked from time to time and replaced at the time and mileage intervals provided by the manufacturer. Some older vehicles may also come with grease fittings on some steering components, which allow for keeping them properly lubricated. In some cases, there are threaded plugs on specific steering system components, which can be replaced with grease fittings to keep these parts properly lubricated and prolong their service life.
If you work on your suspension or steering system, proper wheel alignment should be done every time you replace any parts and components that affect the vehicle’s ride and geometry.