Before you invest in a caravan it's important to understand the basic features of a van and to be aware of important guidelines. Armed with the right information, you can check the various essentials such as tyres, brakes, lights and more.

This brief guide includes the regulations that govern caravans in Australia.

Wheels and tyres

Light truck radial tyres are usually the best for caravans. However, it is crucial when fitting these tyres, that heavy-duty wheels are used, as many light car wheels are not strong enough to support heavy tyres, particularly if they also have to support a fully packed trailer that weighs more than 750kg.

Many trailers have incorrect tyres fitted when new. For instance, AL-KO rubber type suspension units are designed to run radial tyres, but many of them have cross-ply tyres fitted, causing peculiar wear problems and instability.

Always remember that caravans with single axles often carry as much mass on two wheels as a small/medium size car carries on 4 wheels.

Mass and speed ratings

Wheels and tyres that are fitted to a caravan must have mass and speed ratings which are adequate for the maximum legal load that the van is designed to carry. They must also be able to handle the maximum speed that the trailer can be legally towed.

Mass and speed ratings are indicated on the tyre sidewall and are usually coded in the tyre size designation. Some tyres will specify the rating around the inner part of the tyre wall close to the bead of the tyre and the wheel rim. In these cases the rating will be clearly spelt out in full. Those tyres that specify the rating within the tyre size designation require decoding. Refer to Your local tyre dealer or NRMA's Technical Advisory Service.

Light truck tyres are generally specified in the tyre size designation with the letters LT. Example 175R14LT.

Caravans manufactured after July 1, 1990 must be fitted with a tyre placard stating: rim profile, inflation pressure, tyre speed rating and load capacity of each axle group.

Note: The GTM of any trailer must not exceed the total sum of the tyre mass ratings.

(GTM - Gross Trailer Mass is the total permissible weight that can be supported by the wheels of a trailer, not including the weight supported by the towball.)

Suitability of retreads

Retread tyres are commonly used on trailers and provided they are of good quality, complying with Australian Standard 1973-1985, they should be satisfactory for trailer operation. However, if the trailer is to be used for sustained high speed, as on a freeway or motor way, retread tyres are not recommended.

Mudguards

Wheel guards must protect all trailer road wheels. They must be designed to prevent objects being thrown up by the tyres, and to stop people contacting the moving wheels.

Mudguards should be set up in the following way:

• They must be securely fitted and cover the full width of the tyre.
• The bottom edge of the mudguard must not be any higher from the ground than 1/3 of the horizontal distance between the centre of the axle and the mudguard.
• The lower end of the guard or mudflap need not be lower than 230 mm from ground level.

Tyre pressures - do-it-yourself check

It is impossible to list the correct pressures for every caravan, due to variation in size, load, etc. This easy check will help you find the best pressure for your caravan tyres.

• First inflate the tyres to the pressure recommended by the manufacturer of the trailer or the tyre you are using. Secondly, tow your trailer for a distance of 100 km, preferably on a highway.
• Recheck the tyre pressures immediately after pulling over and compare them with the pressures you had at the start of your run. If the pressures are right, the hot readings should be 4 psi (28 kPa) higher than the cold readings.
• If there is a greater than 4psi (28 kPa) difference between these pressures, the tyre temperature is too high and the pressure needs to be increased. If there is less than 4 psi (28 kPa) difference, the pressure needs to be lowered.
• Large 4WD tyres will have a differential of 6 psi (42 kPa).
• Be sure to use the same accurate gauge for both readings.

Brakes

Caravans need their own braking system which is usually connected to the towing vehicle's braking system so both sets of brakes work in tandem.

There are three basic braking systems: electric, override and vacuum and of these, electric brakes are the most cost effective. They are strongly recommended for loaded caravans from 750 kg to 2000 kg. For some larger trailer units, the older vacuum assisted system may be more suitable.

You'll find that caravan brakes have particular requirements. This section includes NRMA Motoring & Services recommendations on areas such as parking brakes, breakaway braking systems and brake controllers.

Electric brake system

This system is the most popular trailer brake system used at present and is the easiest to fit and operate.

This system is normally used on trailers with a laden mass of 750kg to around 2000kg. The system is comprised of a wheel brake system, which is applied by electro-magnets combined with the rotary action of the wheel.

The braking system is connected through the stop-light switch of the towing vehicle. The trailer brakes can be applied simultaneously to car brakes in a pre-set ratio or they can be operated independently through the control unit (see Brake controllers below) that must be fitted in the driving compartment of the towing vehicle.

Override braking system

This system is generally used on single axle trailers up to 1000kg when fully loaded. The caravan brakes are applied automatically by a sliding coupling between the trailer and the towing vehicle. When the towing vehicle's brakes are applied the trailer continues to travel forward which presses on the sliding coupling which in turn mechanically applies the trailer brakes either through a cable/rod link or a hydraulic system.

Vacuum operated braking system

This system uses a vacuum and is usually installed on trailers that have a loaded weight over 1000kg.

The vacuum is created from the inlet manifold of petrol engines and the vacuum pump on diesel engines and stored in a small vacuum tank.

The brake control is wired into the towing vehicle's stop light circuit or hydraulic brake circuit so trailer brakes can be applied simultaneously to and in a pre-set proportion with the towing vehicle's braking system.

The trailer brake system can also be operated independently of the towing vehicle's footbrake. The control unit in this system supplies vacuum via a hose system to a vacuum unit on the 'A' frame of the trailer, which in turn operates the trailer brake system either by mechanical or hydraulic means.

Brake controllers

Electric and vacuum brake systems require a separate controller mounted where the driver can access it readily. This controller allows the driver to set the ratio of braking between the car and the trailer, applies the trailer brakes when the tow vehicle's brakes are applied and enables the trailer brakes to be applied manually.

The most effective controller will give you the following:

• It will allow the operator easy access to all adjustments.
• It will be simple to set.
• It will allow full trailer braking when the manual brake lever is operated.
• The controller will be compatible with two and four wheel braked trailers.
• It will effectively sense the deceleration rate of the vehicle combination for safe and effective trailer braking.

Brake requirements

All trailers built prior to July 1, 1990 that need a brake system, must be fitted with a parking brake that will hold the laden trailer on an 18 per cent incline. We highly recommend this for all trailers with brakes.

A trailer built after July 1, 1990 with an ATM exceeding 2.0 tonnes (2000kg), must have brakes that operate on all wheels. Trailers with a GTM between 750kg and 2000kg require an efficient brake system. For trailers with multiple axles, brakes on at least one axle only, are considered efficient. We recommends that brakes be fitted on all axles.

All independent braking systems must be operable from the driver's seat of the towing vehicle.

A breakaway brake system, which automatically applies and holds the trailer brakes for at least 15 minutes when the trailer is detached from the towing vehicle, must be fitted when the trailer GTM exceeds 2.0 tonne.

The GTM for trailers built before July 1, 1990 can be calculated using the lesser of the following options:

• The sum of the tyre capacities
• The sum of the axle capacities or,
• The sum of the suspension capacities.
• Trailers fitted with electric brakes must display a label stating 'The towing vehicle must be equipped with a compatible control system'.

ATM - Aggregate Trailer Mass is the total laden weight of a trailer, including the towball mass, usually specified by the manufacturer. However, State regulations must also be considered in relation to this figure.

GTM - Gross Trailer Mass, the total permissible mass which can be supported by the wheels of a trailer, not including the mass supported by the towball.

Suspension

Semi-elliptic leaf spring/straight axle system
Many experienced trailer operators prefer these suspension types. This is because they can be temporarily repaired if they fail in remote areas.

Trailing arm or coil spring suspensions
When most trailing arm and coil spring suspensions are combined with quality shock absorbers they need little or no attention. They have superior design and operation, create comfort and stability and give a better ride than older versions mentioned above.

Rubber suspension systems
This specially formulated rubber unit gives excellent ride and stability and is ideal for trailers with a low centre of gravity and low ground clearance.

Special care needs to be taken with this type of suspension. Make sure it has been correctly specified for the laden mass of the trailer and that it is used in conjunction with light truck radial tyres. Replacement or repair of this kind of suspension can be quite expensive.

Your caravan dealer will give you information on the suspension of a caravan and they should provide advice on the right suspension for the kind of travelling you have planned.

Axles

The number of axles fitted to a trailer unit can greatly affect the handling, stability and tyres. A caravan with considerable overhang from the centre of the axle assembly to its rear will have a greater tendency to sway and may be unstable.

Safe axle measurements - what you need to know

• As a general rule, trailers 5 metres (16 ft) in length and over, will be far superior in all aspects of towing if two or more axles are fitted.
• Light trailers may have up to and no more than three axles fitted in a group in one location. The centre of the axle or axle group will normally be slightly rearward of the centre of the trailer body.
• If two axles are fitted, they must not be more than 2 metres apart.
• If three axles are fitted they must not be more than 3.2 metres apart, overall.
• Where two axles are between 1 metre and 2 metres apart, or three axles are between 2 meters and 3.2 metres apart, they must be interconnected by a load sharing suspension of an approved type.
• Load sharing suspensions are designed so that each axle in a multiple axle group carries the same mass regardless of the terrain over which the trailer is travelling.
• Where two or three axle groups are less than the above distance apart, load-sharing suspensions are not required.

Shocks in the system

Shock absorbers are normally fitted to most independent suspension systems and can be added to leaf spring suspensions in most instances. The addition of shock absorbers can make a considerable difference to the handling qualities of a trailer unit.

Lights and indicators

Several laws apply to lights on a caravan, in much the same way as laws apply to the lights on a car. The rules for caravans and trailers changed on the July 1, 1990. We have given the rules for lights before and after this date because trailers or caravans registered before July 1, 1990 can follow the previous rules. Any vans that have are registered after this date must comply to the post July 1, 1990 rules.

As a general rule, all lights on a caravan must operate at the same time as the corresponding lights on the towing vehicle.

Brake lights

All trailers first registered on or after July 1, 1987 must have two red brake lamps, one fitted on each side of the rear of the trailer and at equal distances from the trailer's centre-line. Brake lamps must be fitted not less than 350 mm or more than 1500 mm from ground level and must operate when the towing vehicle's brakes are applied and when the trailer brakes are applied independently.

Reflectors

Before July 1, 1990

AIS 24 rule
All trailers must be fitted with two red reflectors at the rear, one on each side of the trailer at equal distances from the centre line and not more than 1 metre from the ground. If the trailer width is in excess of 2.2 metres, the reflectors must be fitted within 250mm of the widest point of the trailer. If the width of the trailer is less than 2.2 metres, the reflectors must be fitted within 400mm of the widest point. Reflectors must have a minimum reflective surface area of 2500mm.

After July 1, 1990

VSB No 1 rule
Rear red reflectors and front white reflectors are to be fixed at a height between 350 and 900 mm, no closer together than 600 mm and no further than 400 mm from the trailer's outer edge at the rear, and 150 mm at the front.

Sufficient amber coloured reflectors should be fixed to the trailer's side between 350 and 900 mm in height, within 3 metres of the towball at the front and 1 metre of the rear of the trailer and no further than 3 metres apart.

Direction indicators

Before July 1, 1990

AIS 24 rule
Direction indicators must be fitted on any trailer where its load obscures the rear indicators fitted to the towing vehicle, or it has a total length, including the towing vehicle, over 7.5 metres. The direction indicators must be amber in colour and spaced equally from each side from the centre line of the trailer, within 500 mm of the outer extremity of the trailer and not more than 2 metres or less than 400 mm above ground level.

After July 1, 1990

VSB No 1 rule
Two amber direction lamps must be fitted at the rear of the trailer, at a height of between 350 and 1500mm, no further than 600mm apart and within 400mm of the trailer's outer edge. The trailer's indicator lights must also operate with the tow vehicle's hazard lights.

Flashing rate

Indicators must flash within a range of 60-120 flashes per minute and must incorporate a visible or audible telltale system that indicates to the driver that the trailer's direction indicators are working correctly.

Combination lights

Tail, brake, number plate and turn indicator lamps may be combined with reflectors, in a single unit, providing they meet each of the individual lamp's requirements.

Tail light

Before July 1, 1990

AIS 24 rule
At least one lamp must be fitted to the rear of a trailer, either in the centre at the rear or the right hand side. The light must be red in colour and if two lamps are fitted they must be equal distances from the trailer's centre line and no more than 1 metre from the ground.

After July 1, 1990

VSB No 1 rule
Two red lamps, must be fitted at equal distances from the trailer's centre-line, no closer than 600mm apart, no further than 400mm from the outer edge of the trailer at a height between 350 and 1500mm and operate concurrently with the tow vehicle's lights.

Number plate light

Before July 1, 1990-

AIS 24 rule
A white light must be fitted to illuminate the number plate, making it clearly visible at night. This light may be incorporated in a tail lamp, providing the white light is directed onto the number plate and does not show white light rearward of the vehicle.

After July 1, 1990-

VSB No 1 rule
The number plate light must not be greater than 7 watts in power, enable the number plate to be clearly legible from a distance of 20m and operate concurrently with the tow vehicle's number plate light.

Clearance and side marker lamps

Before July 1, 1990-

AIS 24 rule
Any trailer that is 2.2 metres or more in width or projects more than 150mm beyond each side of the towing vehicle, must be fitted with clearance and side marker lamps within 150mm of the outer extremity of the trailer. The rear lamps must not be lower than 600 mm or higher than 1.5 metres from the ground. Clearance lights showing light only to the front of the vehicle must be amber in colour, while those showing light to the rear only, must be red in colour. However, those lamps on the side of the trailer must show amber light to the front and red light to the rear.

After July 1, 1990

VSB No 1 rule
Two clearance lamps showing white at the front and red at the rear must be fitted to each of the front and rear panels, as high as possible and within 400mm of the outer edge of any trailer over 2.1 metres wide. Trailers over 2.1m wide or total length over 7.5m must also have side marker lamps, each showing amber to the front and red to the rear. They must be mounted on the side within 300 mm of the front and rear, and at a height of between 600mm and 1500 mm. If over 7.5m in total, an additional lamp must be fitted midway between them. Boat and similar construction trailers must have their side lamps as close to the front and rear of the trailer as possible, and if the two lamps are less than 2.5m apart, lamps at the rear only are acceptable.

Electrical wiring and connections

All wiring must be securely anchored to the chassis of the trailer at intervals of no more than 600mm, with all connections and terminals securely attached and insulated. All wiring must be protected where it passes through body or chassis members, to prevent it from chaffing.

A proper earth return wire must be provided, as it is not permissible to use the trailer coupling for this purpose.

All trailers and towing vehicles registered for the first time after 1st January 1988 must use electrical connectors that comply with Australian Standard 2513-1982, ie minimum 7-pin connector.

Electrical connections

Two basic types of electrical fittings, one round and the other flat, are available for light trailer use. A trailer socket can be flush or surface mounted and usually has 6, 7 or 12 pins. Seven pin connectors are mandatory on all new trailer units first registered after January 1, 1988, allowing sufficient connections to cope with all lighting requirements and electric brake controls.

Vehicles first registered before January 1998 commonly use a six pin electrical connector and some vehicles requiring more than the mandatory seven connections may be fitted with a twelve-pin connector.

Since the introduction of the mandatory seven-pin connector, all wiring connections have been standardised and the use of a specific trailer cabling involving seven wires and standardised colouring has also been adopted. A wiring connection and colour guide is provided below for 6, 7 and 12 pin connectors.

6-pin round connector

Colour	Connect to -	Pin
Brown	Tail, licence & clearance lamp	1
Yellow	Left flasher lamps	2
Green	Right flasher lamps	3
Red	Stop lamps	4
Blue	Auxiliary circuit	5
White	Ground/Earth	6

7-pin round/flat connector

Colour	Connect to -	Pin
Yellow	Left flasher lamps	1
Black	Reversing lamps	2
White	Ground/Earth	3
Green	Right flasher lamps	4
Blue	Service/trailer brakes	5
Red	Stop lamps	6
Brown	Tail, licence & clearance lamps	7

12-pin round/flat connector

Colour	Connect to -	Pin
Yellow	Left flasher lamps	1
Black	Reversing lamps	2
White	Ground/Earth	3
Green	Right flasher lamps	4
Blue	Service/trailer brakes	5
Red	Stop lamps	6
Brown	Tail, licence & clearance lamps	7
Orange	Battery charger/Electric winch	8
Pink	Auxiliaries, etc./battery feed	9
White	Ground/Earth	10
Grey	Rear fog lamp	11
Violet	Spare	12

Mirrors

A number of additional extension mirrors can be purchased for towing a caravan. If you are unable to see the rearmost corner of each side of your van, when it is fully loaded with the existing exterior mirrors, then you will need to use additional mirrors to increase your rear vision.

Various types of add-on mirrors are available including extension mirrors to add to your existing exterior mirrors, door mounted mirrors, guard mounted mirrors, bonnet mounted mirrors and mirrors that can be attached to the roof rack of your vehicle.

Various combinations and situations will have a bearing on the kind mirror that will suit your car. It's important to think about the distance between the mirror head and the driver as when this length increases, the visible area in the mirror diminishes.

The mirror also needs to be secured firmly to avoid 'jiggling' and distortion of the viewing area. Door-mounted and clamp-on mirrors which attach to the existing exterior mirrors are usually the best. Good mirrors can be expensive but they are effective and of high quality.

Source: Towing in Australia, Pub: NRMA Automotive technical Services