An often-overlooked safety measure before hitting the road is checking tyre pressure, in both your car and caravan. A road trip in Australia will provide the opportunity or even necessity to traverse an array of surfaces, from bitumen through to mud and perhaps even snow. When you think about it, tyres are the only part of your vehicle in direct contact with the ground. Your vehicle needs correct surface contact to adequately steer, accelerate and brake.
Despite experts differing slightly when it comes to the exact numbers with tyre inflation, they certainly all agree that having the correct tyres fitted and inflated to the correct pressure is crucial. The Caravan Council of Australia warns that wrong tyres or the right tyres inflated to the wrong pressures can lead to swaying and roll-overs
A good place to start is with the purchase of your own tyre pressure gauge. This way you can manage the tyre pressure yourself at any stage of your trip. Increasing and decreasing tyre pressure accordingly is paramount to the safety of those in and around your vehicle. It’s also essential to have a quick deflator and a powerful pump/air compressor because despite the time and effort, you will need to deflate and inflate depending on your terrain.
It is recommended that any change in tyre type or size first involves consultation with the tyre or caravan manufacturer. It’s important that tyres of the correct specification be fitted, with the same construction of tyres on all wheels, along with tyre pressure across an axle being equal. Pressures should be checked and adjusted prior to any journey when the tyres are cold. Reducing pressures on warm tyres could result in them being too low once cooled down. Tyres not inflated to the correct pressure also wear out more quickly.
Sand can vary rapidly in patches and heat is quickly built up with constant resistance to tyres. The idea when driving across sand is to glide across the surface, and a tyre inflated to road pressure will quickly sink in soft sand. Deflating the tyre increases the surface area of the tyre and will help to prevent the wheels from spinning and your vehicle becoming bogged. When hitting sand, some experts suggest you can lower the tyre pressure to 10 pound-force per square inch (psi), but a minimum of 16psi is recommended to be safe. Only decrease lower (anything lower than 5psi could result in the rim spinning around the tyre) to move out when bogged, immediately increasing pressure again once clear.
Variables such as slope steepness, mud-type and the surface underneath mud play a factor and you might not even have to lower pressure. Watery mud with a solid base allows for higher pressure but thick mud with a deep base that’s loose requires lower pressure. It’s crucial to maintain momentum and traction but remain in control to avoid vehicle and environmental damage.
When driving on other off-road surfaces, the general idea is the same. Low tyre pressure will assist with traction and prevention of damage to the tyre and vehicle. The increased traction will make it harder for the wheels to spin. The lower pressure allows for the tyre to form around logs, rocks and holes. It also helps with the prevention of punctures from sharper objects. Reducing the inflation pressure reduces that tyre’s loading capacity, and with any terrain, higher pressure is required when carrying heavy loads.
A general guide to tyre pressure:
*This is intended strictly as a guide only
Pressure 36 to 40psi
Speed range 90 to 110kph
Good unsealed roads:
Pressure 30 to 34psi
Speed range 70 to 90kph
Rough unsealed roads:
Speed range 50 to 70kph
Rough track – mud, rocks, creek crossings:
Pressure 20 to 23psi
Speed range 10 to 50kph
Pressure 16psi (10 to 14psi if in strife)
Speed range 20 to 30kph
A reduction of 4-5psi is generally noticeable to the naked eye, which coincidentally is the psi difference recommended for the front (lower) to the back (higher) of your vehicle when towing a caravan due to the heavier loading at the rear. Be wary of any 4WD vehicle placards recommending anything below 30psi on bitumen roads. You may notice this with some older vehicles but the supposed added smoothness to your ride can be dangerous and will most definitely result in disappointing tyre life.
It is important to know the laden weight of your caravan, which can easily be achieved through a weighbridge. Your empty vehicle or caravan’s weight is known as tare weight. Subtracting your tare weight from your laden weight determines the weight of your load. A simple maths equation to identify individual tyre loads is to divide the laden weight by the number of tyres on your caravan. As a general tip, allow around 15 per cent margin for safety with all weight measurements. Remember that caravan tyres wear a lot quicker than car tyres due to the loadings they are subjected to. Consult your tyre specialist should you think wear is premature or uneven but it is usually attributed to under-inflation and/or overloading.