Once you've selected the optimum tyre for your driving usage whether it be HT, AT or MT, you need to understand some basic rules for obtaining maximum longevity from your tyre investment plus you need to observe some safety issues regarding tyre pressures when travelling.
Most tyre manufacturers recommend that 4WD tyres are rotated every 10,000km (
check these specifics with your supplier as warranty conditions may be affected). Rotation is important in a 4WD vehicle because each tyre will wear differently due to breaking, cornering and weight distribution factors. If the vehicle operates in constant 4WD, all wheels are driving wheels, but if not, then whichever are the driving wheels (front or rear wheel drive) will also wear quicker. The more evenly your tyres wear, the longer life you should achieve. Obviously it goes without saying that tyre pressures should be regularly checked for the same reasons.
When travelling on dirt roads with a heavily loaded vehicle (usually adding weight above the standard vehicle's tyre-rated load capacity), a few important rules need to be observed:
To ease the comfort of the ride and to aid in traction on particularly bad corrugations, it is best to reduce tyre pressures about 4 -6 psi lower than what you run on the bitumen with this same load. Very stony country, such as the
Birdsville Track, can handle even softer tyre pressures. This may not seem to make sense at first, but if you consider that your tyre is just like a balloon being bounced over sharp objects then you can see how the higher pressure would make it more prone to "popping" - termed by tyre manufacturers as stone fractures. This is most common reason for flat tyres occurring on outback roads and can be easily avoided by reducing tyre pressures.
It is also far preferable to keep speed constant and if possible around 85km/hr over corrugated roads (presuming the road is free from washouts and corners and it would otherwise be safe to do so). You will find that you can "ride" over the worst of the corrugations, provided your tyre pressures are reduced as suggested above. Any faster can be dangerous, slower and the corrugations may shake you and your vehicle to pieces. If handling of your vehicle appears poor, then a good look at
suspension might be prudent. The best indication is "bottoming-out" when travelling as per the above suggested optimums. Most 4WD vehicles do not come with a
suspension system that is rated to handle the load that is carried for extended trips (ie. water, fuel, supplies and spares). The correctly rated
suspension-weight load ratio will also aid in improved tyre wear and longevity.
There is no perfect tyre or tyre pressure and a combination of speed and driver skill (plus a little bit of luck) will be the secret to minimising flat tyres and maximising tyre wear.
Tyre pressures are best checked when cool, because hot tyres give an incorrect reading. And don't forget that tyres on an off-road trailer can be inflated and deflated to suit conditions as you would your vehicle.