Is the directional control of your vehicle.
The wheel is always set to the side of the vehicle which is towards the middle of the road. This will give you a better view of the road ahead and a respect for the oncoming vehicle.
By working through the front wheels you will always steer to the direction you want to move, this applies in reverse as well.
The turning of the steering wheel and its relationship to how far your vehicle wheels are turned is called the steering ratio.
Vehicles that are to be raced will have a much more responsive steering than a public road going one. On a race track you will not have oncoming vehicles to worry about.
When steering you must remember that there is only a limited amount of grip available from your tyres.
Steering while braking or accelerating it is not always avoidable; it should be done as part of a well developed driving plan and with caution.
Swing Beam Steering.
With horse and cart steering was achieved by turning the front axle about a central pivot. This is called `swing beam steering` and has a number of disadvantages. You need room under your vehicle (or horse and cart) for the axle to swing round. As a result of a lack of room this limits the amount of steering lock and hence manoeuvrability of your vehicle.
Or you can create the room and limit the load carrying ability of your vehicle. Either way your vehicle is prone to bumps and holes in the road as your wheels are directly connected to the cart.
Another problem is that the outside wheel is turning a bigger circle than the inside one, which is inefficient.
The main advantage of swing beam steering is that a line drawn through the front (steering) axle will intersect with a line drawn through the rear axle. This gives the turning circle of your vehicle which will have the path of least resistance.
Ackerman Steering.
The problems of swing beam were solved for horse drawn carriages in 1815 by what is now known as Ackerman Steering. This allows the 2 front wheels to turn different radii but both to have the same point of intersection. This is achieved by allowing the two front wheels to turn separately but to the same purpose. This allows greater manoeuvrability of your vehicle. It is easier to steer and this results in less tyre wear.
Rear Wheel Steering.
When moving forward and the steered wheels are leading, your vehicle pivots about the centre of the turning circle. This is where a line through the front wheels intersects a line through the back wheels.
When moving forward and the steered wheels are trailing, your vehicle will now pivot about the front wheels. This makes your vehicle highly manoeuvrable and as such unsuitable for the public highway. Specialist vehicles such as fork lift trucks that need to manoeuvre in a confined space will be rear wheeled steered.
Some large vehicles may have a very limited rear wheel steer in order to make them more manoeuvrable.
When the steering is too sensitive and reacts to small movement it may place your vehicle in the path of oncoming vehicles. The speed of a car will magnify the effect of the steering.
Steering in Reverse.
When steering in reverse your steered wheels are now trailing and you will pivot about your back wheels. When steering in reverse you are now steering in the direction of your intended travel.
So to move in you must steer in and to move out, steer out. Remember that your front end will swing out in the opposite direction to where you are steering.
Steering Ratio.
Two wheeled vehicles such as bicycles have a steering ratio of 1:1. Turn your handle bars 30 degrees to the left and the bike’s front wheel moves 30 degrees to the left.
In modern motor vehicles the steering ratio is set between 12:1 and 20:1. With a low steering ratio you have a more responsive vehicle but the effort required to turn the wheels is greater. The more responsive your steering, the greater the chance a sudden jolt could put you in the path of an oncoming vehicle.
Sport cars will have lower steering ratios. A higher steering ratio will be less responsive but safer at higher speeds. In addition it will require less effort to turn. These ratios will be found on Lorries and other large vehicles.
Variable-ratio steering is used with rack and pinion type steering. It starts with a high ratio giving safety at speed but as the lock goes on the ratio decreases giving more maneuverability. This is done by the spacing of the teeth on the rack as it is turned by the pinion.
Understeer, Oversteer and Dry Steering.
Understeer and oversteer are terms relating to how your vehicle steers. These are general terms meaning how someone might be describing the sensitivity of the vehicle’s steering.
But there is also the technical meaning which relates to the vehicle dynamics. This is how your vehicle is loaded, your driving technique, the road and conditions, tyre pressures, the steering geometry and how they all interact.
The more aggressively your vehicle is driven the more likely you are to experience a loss of grip from either the front or rear tyres.
Going wide is understeer which is when your front wheels are losing traction. As the front wheels lose traction the steering effect is not apparent.
The rear end spinning out is oversteer and this is when the rear wheels have lost traction. As the rear wheels lose traction the steering effect is greatly exaggerated.
Oversteer.
Oversteer is when turning into a bend your rear wheels are trying to turn a wider turning circle than the front wheels. This means the front of your vehicle is trying to turn a tighter circle than the back which may result in losing the rear end. This is quite often due to a loss of traction at the rear end.
Counter steering is controlled use of oversteer to go round bends. This is sometimes known as a power slide. The driver is still in control and able to accelerate out of the turn.
Understeer.
Understeer is when your front wheels are moving in a wider turning circle than the rear ones. This happens when the front tyres are losing grip and results in going wide on bends and corners.
Dry Steering.
Dry steering is when you are stationary and are turning your wheels. This puts extra strain on the steering mechanism and may lead to flat spots on your tyres.
The Steering Wheel
This is the means by which your desires regarding position are transmitted to the driving wheels. It also gives mechanical advantage which enables the driving wheels to turn more easily. The bigger the wheel the easier it is to steer.
The greater the steering ratio the easier it is to turn the driving wheels. The steering wheel serves a number of important active and passive safety functions.
Passive Safety:
- This is by providing the driver with a means of bracing himself in case of a collision.
- By holding the wheel correctly the driver is able to control the vehicle if anything happened to one of the wheels.
- This could be a blow out or one of the wheels striking an object in the road.
- Every time you take a hand off the wheel you are in less control of your vehicle.
- The steering wheel is normally cushioned so in any accident it is less likely to injure the driver.
- On most modern vehicles it will also contain an airbag.
Active Safety:
- This is done by giving access to warning instruments.
- These are the horn and the light stick for flashing the lights.
- These can both normally be done without the need to remove hands from the wheel.
- By allowing access to other controls.
- Some vehicles use a paddle change on the steering wheel for gear change, normally sports cars.
- By giving access to ancillary controls like the radio.
Using the Wheel.
Correct use of the steering wheel is dependent on proper seating position. The right seating position will aid active safety. This is done by allowing the efficient function of the seat, seat belt, airbags and use of the steering wheel. One is dependent on the other.
Holding:
- The correct way to hold the wheel is: with your hands at 10 to 2 or at ¼ to 3.
- So that way you are braced to the top half of the wheel in the event of an unexpected collision.
- Your hands are in the correct position for push-pull steering.
- If you need to take evasive action by rotational steering you are able to do so.
Hold the wheel with your thumbs along the rim of the wheel and a light grip with your fingers:
- This will help you get a feel for how your vehicle responds.
- If the wheel kicks for any reason you will not have your thumbs damaged by the spokes.
- In the event of a collision your hands followed by your arms will go to the outside of the wheel.
Your wrists should be straight
- This will reduce the possibility of repetitive strain injury and driver fatigue.
- In the event of a collision your wrist will not be damaged.
Your elbows should be slightly crooked:
- When your arms are held straight for steering you will not have the same control as when they are slightly crooked.
- In the event of a collision your elbows could possibly be broken if they are locked out straight when trying to brace.
- Your arms are stronger in contraction than extension hence should be crooked when holding the wheel.
Steering
Steering on a public road going vehicle is set up to be safe. It will allow you to deal with oncoming vehicles and other road users. It does this by being less responsive than racing or rally cars.
This is achieved 3 ways.
Firstly: the steering methods of the driver.
- These should allow for the unexpected such as the wheel kicking or having to swerve for another road user.
- Push-pull
Secondly: the steering ratio of the wheel.
- A high ratio makes your vehicle more stable while being steered.
- You are less likely to move into the path of an oncoming vehicle if the wheel kicks for any reason.
- But you are slower into turns which give you more time for observations.
- A low ratio may be used on sports cars and when racing to make you quicker into turns.
Thirdly: by the steering geometry which is how your vehicle is set up.
- Vehicles for the public road are set to be safe.
- A question on an insurance application is has your vehicle been modified?
- An undeclared modification may invalidate your insurance.
- Some of the things that go into steering geometry are toe angle, castor, camber and the tyre type pressure etc.
- Beware of cars previously owned by boy racers.
Steering Methods
These are fixed input, push-pull and rotational.
Fixed Input Steering:
- This is when you have both hands on the wheel and are making minor adjustments to your position.
- It gets you to where you want to be.
- With both hands on the wheel, keeps you safe as you get there.
Push-pull Steering:
- This is your working steering.
- Fixed input steering allows you minor corrections, it is push-pull that gets you round obstructions, corners and helps you to manoeuvre safely.
- This is normally taught by professional driving instructors to their pupils.
- This method is also known as feeding the wheel.
- Feeding describes the way it is fed from one hand to the other.
- Because your arms are never crossed this gives greater control if the wheel ever kicks or in the event of a collision.
- When using push-pull; always commence with the pull action first.
- This is an easier movement and gives more control than pushing the wheel up.
- When taking emergency action when using push-pull steering, you have the option of rotational steering (swerving).
- This may not be available with your arms crossed.
- Your vehicle will have to move slower in order to use push-pull.
- This has the huge bonus of giving you more time for observation both when manoeuvring and turning corners.
- Being slower and taking the time for observations will make you a much safer driver, particularly at junctions.
Rotational Steering.:
- This is a swerve to be used in an emergency.
- Because your hands are crossed you have no further option of swerving.
- If you are crossing your hands when routinely turning corners, you will have a very limited swerve capacity when turning.
Syllabus For Learning To Drive – Car Controls & Instruments
© Liam Greaney
