Why do some cars respond so well to the driver? Great handling makes you feel safe and in control – and makes panic swerves and steering corrections as effective as possible. The lightest touch of the wheel should direct the steering system effortlessly and precisely.
As well as a well-designed suspension, it takes a good quality steering system and steering parts to achieve excellent handling. If you’d like to know the anatomy of a steering system and how it supports handling, road holding and driveability, here is an easy overview.
What is a Steering System?
The steering system of your car is everything from the steering wheel to the steering shaft, rack and pinion (also known as the gearbox), all the way to the linkage which connects to the wheels themselves.
A steering system must turn the front wheels in the direction you wish to go but it must also do so accurately and effortlessly.
It uses gears to accomplish this last goal with the result that on most systems, it takes around four turns of the steering wheel to turn the front wheels just a few degrees from far left to far right.
The precise number of steering wheel turns can differ between cars, with sports cars typically requiring fewer, and family cars more.
This relationship of steering wheel effort to road wheel response is called the ‘steering ratio.’ It’s calculated by dividing 360 degrees, or one complete turn of the steering wheel, by the number of degrees the wheels turn left or right.
So, for example, if they turn 20 degrees, the ratio is 18:1, expressed as ‘18 to one’. The lower the ratio, the quicker the steering response, and vice versa.
However, even on a car with a high steering ratio that takes less effort, you’ll still find it next to impossible to turn the steering wheel. That’s why steering systems are power-assisted.
That all this twirling feels so connected is down to the way the steering system is constructed and the fact that it can allow for movement of the wheels and the suspension without disturbing it.
How does the steering system work?
The steering system converts the rotation of the steering wheel into a swivelling movement of the road wheels in such a way that the steering-wheel rim turns a long way to move the road wheels a short way.
The system allows a driver to use only light forces to steer a heavy car. The rim of a 15 in. (380 mm) diameter steering wheel moving four turns from full left lock to full right lock travels nearly 16 ft (5 m), while the edge of a road wheel moves a distance of only slightly more than 12 in. (300 mm). If the driver swivelled the road wheel directly, he or she would have to push nearly 16 times as hard.
The steering effort passes to the wheels through a system of pivoted joints. These are designed to allow the wheels to move up and down with the suspension without changing the steering angle.
They also ensure that when cornering, the inner front wheel – which has to travel round a tighter curve than the outer one – becomes more sharply angled.
The joints must be adjusted very precisely, and even a little looseness in them makes the steering dangerously sloppy and inaccurate.
There are two steering systems in common use – the rack and pinion and the steering box.
On large cars, either system may be power-assisted to reduce further the effort needed to move it, especially when the car is moving slowly.
Types of a Steering System
Before we head into the explanation there are currently two major types of the steering system. The commonly used Rack and Pinion System and the conventional system know as the Recirculating Ball Steering System. We will explain both in brief and also how the power-assisted steering system works which is commonly called power steering.
Rack And Pinion Steering System
In most cars, small trucks and SUVs on the road today, there is a rack and pinion steering system. This converts the rotational motion of the steering wheel into the linear motion that turns the wheels and guides your path.
The system involves a circular gear (the steering pinion) which locks teeth on a bar (the rack). It also transforms big rotations of the steering wheel into small, accurate turns of the wheels, giving a solid and direct feel to the steering.
power steering
It’s likely that if you drive today, you’re used to power steering. Contemporary cars, and especially trucks and utility vehicles have a power steering system function – also called power-assisted steering.
This gives that extra energy (either hydraulic or electric) to help turn the wheels and means parking and manoeuvering requires less effort than with simple manual force. The rack and pinion steering system is slightly different with power steering, with an added engine-driven pump or electric motor to aid the steering assembly.
So is ease the only benefit of power steering? The system allows you to have higher gear steering and means you have to turn the steering wheel less to turn the wheels further (less steering wheel turns lock-to-lock).
It therefore sharpens up response times and makes the steering even more precise. With such busy roads and traffic jams, this means drivers can more safely manoeuvre in close proximity to other vehicles. Keeping tight control at all speeds, in any conditions and in critical situations, will help to avoid accidents.
Recirculating-Ball System
This system is much less common on cars because it’s less sensitive and more complicated than a rack and pinion system. Instead of a pinion gear and a steering rack, it uses a so-called ‘worm gear’, to which the steering column is connected.
This worm gear has a thread cut into its exterior and passes through a block of metal called the nut that has a corresponding thread on its inside walls.
Where the nut and the worm gear mesh, ball bearings, intended to reduce friction as well as take up any slack as the worm gear turns, pass up and down the channels created by the threads.
As the balls exit, they are channelled back to the top, giving rise to the term, ‘recirculating ball’.
The nut also has teeth cut into the outside of it which engage with teeth on one end of an arm, called the Pitman arm.
This is connected to the steering linkage which has, at either end, track rod ends attached to the wheel hubs. As the steering wheel is turned, so the worm gear turns the nut which turns the Pitman arm, which moves the linkage and turns the wheels.
Parts of a Steering system:
The parts of a steering system are listed below. They are:
- Steering wheel
- Steering column or shaft.
- Steering gear
- Drop arm or pitman arm
- Ball joints
- Drag link
- Steering arm
- Stub axle
- Left spindle and kingpin
- Left tie rod arm
1. Steering wheel:
The steering wheel is the control wheel to steer a vehicle by the driver. It contains a traffic indicator switch, light switch, wiper switch, etc. It is also called a driving wheel or a hand wheel is a type of steering control in vehicles.
Steering wheels are used in most modern land vehicles, including all mass-production automobiles, as well as buses, light, and heavy trucks, and tractors.
2. Steering column or shaft:
The Steering column also known as the shaft is fitted inside the hollow steering column. When the steering wheel is turned, the steering shaft will also be rotated. Due to this, the motion is transmitted to the steering box.
The steering column is located at the top of the steering system and attaches directly to the steering wheel. The steering column then attaches to the intermediate shaft and universal joints.
3. Steering gear:
The pitman’s arm is splined to the steering gearbox rocker arm at one end and the other end is connected to the drag link by a ball joint.
The steering gearbox contains the gears that transmit the driver’s steering inputs to the steering linkage that turns the wheels, and it multiplies the driver’s steering changes so that the front wheels move more than the steering wheel.
4. Drop arm or pitman’s arm:
When the steering wheel is turned right or left the pitman transmits the motion it receives from the steering gearbox to the tie rod. A “drop pitman arm” is used to correct the steering when a vehicle has a suspension lift.
5. Ball Joints:
The ball joints are spherical bearings that connect the control arms to the steering knuckles. The bearing stud is tapered and threaded and fits into a tapered hole in the steering knuckle. A protective encasing prevents dirt from getting into the joint assembly.
6. Drag link:
The drag link converts the sweeping arc of the steering arm to linear motion in the plane of the other steering links. “The drag link connects the pitman arm to the steering arm, or in some applications, it connects to the tie rod assembly.
7. Steering arm:
The steering arm is an arm for transmitting the turning force from the steering gear to the drag link, especially of an automotive vehicle.
The basic function of the steering system is to allow the driver to safely and precisely steer the vehicle. Beyond this, the steering system also provides a way to reduce driver effort by making the act of steering the vehicle easier.
8. Stub axle:
When the steering wheel is rotated, the motion is transmitted to the pitman’s arm through the gearbox. This motion is transmitted to the drag link. Drag link transfers this movement to stub axle which rotates about kingpin. This turns the right wheel.
9. Left spindle and king arm:
In automotive suspension, a steering knuckle is that part that contains the wheel hub or spindle and attaches to the suspension and steering components. It is variously called a steering knuckle, spindle, upright, or hub, as well.
The wheel and tire assembly attach to the hub or spindle of the knuckle where the tire/wheel rotates while being held in a stable plane of motion by the knuckle/suspension assembly.
10. Left tie rod arm:
The right- and left-side tie rods are connected to each other by a center link, which is also mounted to the Pitman’s arm on the steering gear and the idler arm on the passenger side of the vehicle.
Rack and pinion steering are currently the most predominant of the two steering linkage systems.
Steering & Alignment
Even when all of the inner workings of your steering system are operating to the best their ability, there’s still one more thing to keep in mind when it comes to steering your car in the right direction: wheel alignment. Safe steering and proper wheel alignment go hand in hand.
When your car was first manufactured, your wheels were pre-set at special angles to keep them running straight and driving smooth. In order for your vehicle to travel and respond to your steering the way it’s supposed to, it needs precise alignment.
Unfortunately, your alignment can get thrown off when you bump into a curb, hit a pothole, or drive on rugged, unmaintained road. Improper alignment can shorten the lifespan of your tires and affect your ability to steer safely and accurately. If your car pulls to the right or the left, your steering wheel is crooked when you’re driving straight, or your tires are squealing, it may be time for an alignment.
What Are Common Issues With A Steering System?
The most common issue you will see with a steering system is a linkage issue. The tie rod or rod end is the main linkage piece that helps you maneuver the vehicle. But when those tie rods wear down, it is harder to maintain proper alignment, and eventually lose control of the steering.
If you are experiencing difficulty handling the steering in your car, it is important to get it checked out by a professional as soon as possible. It is dangerous for yourself and others on the road if you lose control of your vehicle due to a steering issue.
