This article discusses the topic of tyre air pressures used for different types of 4wd applications.
Tyre pressures are a topic regularly debated by 4wd owners. It is certainly true that off-road terrain will alter the performance of your tyres compared to sealed roads and tyre pressures can be adjusted to better suit different terrains. However there are no rules set in stone as to what pressure you should use for what type of terrain.
As a general guideline rougher terrains will be better handled with lower tyre pressures than what is used for highway driving. The main reasons are that by lowering pressures the contact patch of the tread will be increased giving better traction and stability. The lower pressure will also make the tyre less prone to punctures and other damage, the reason being that lower pressure allows the tyre to “give” a little more and any impacts can be cushioned by the tyre.
How low should I go? Again there are no hard and fast rules here. The reason being that every 4wd is different. Even exactly the same 4wd will handle differently depending on the amount and position of weight in and on the vehicle. Some other influencing factors are driving style, weather conditions, suspension setup, etc etc. In reality there are a huge number of factors which can be taken into account when selecting tyre pressures, but a widely accepted view is that the harsher the terrain, the lower the pressure you should run.
Another important consideration when running lower tyre pressures is your speed. Lower pressure will increase the rolling heat generated by your tyres. To ensure this does not lead to overheating you need to reduce your speed to manage the heat generation safely. The lower speed will also provide you with a more comfortable ride and less stress on your tyres and suspension components.
The following picture shows some of the different terrains you may experience and can be used as a guideline to pressure and speed adjustment to suit.