Reducing your tyre PSI for off-roading & 4WD
Changing your tyre pressure is one of the best things you can do to maximise your off-road experience. It’s also one of the most effective ways to alter drivability and performance in 4-wheel drive and off-road situations. If you think about it, the only thing connecting your 4x4 to the ground beneath is your tyres, so the way you inflate (or deflate) your tyres will largely impact the way you drive.
When we talk about air pressure alteration for off-road terrains, we generally mean reducing the PSI. However, it’s important to remember to re-inflate your tyres as soon as you come in contact with the road. This is because reduced tyre pressure at high speeds on hard surfaces like roads and highways is incredibly dangerous and may cause tyre blow-ours from increased heat and pressure.
Tyre pressure on sand
If you’ve ever watched a 4WD across soft sand, you might have noticed mounds of sand building up in front of the tyres. This is caused by the forward motion of the tyres which essentially creates strain on the vehicle as it tries to push itself up and over. If your PSI is sitting at a standard pressure, the sand will continue to be pushed in front of your tyres and force you back down until you get bogged.
On the other hand, reducing your PSI allows you to experience an increased ‘footprint,’ distributing the weight of your car over a greater surface area and therefore preventing your wheels from sinking into the sand. This, in turn, stops the formation of sand mounds in front of your tyres and allows your vehicle to achieve forward momentum with less of the work.
It is important to remember that reducing your tyre pressure will increase your rolling resistance and reduce your fuel economy, so remember to stock up on fuel to avoid making unexpected trips to the service station.
Tyre pressure on other off-road surfaces
Aside from soft surfaces like sand, mud or even snow, reducing your tyre pressure for harder surfaces is also a really great way to improve your experience off the road. As mentioned, reducing your PSI allows you to maximise your vehicle ‘footprint,’ essentially increasing contact with the ground and subsequently increasing traction.
Deflating your tyres to a lower pressure can also allow you to experience a smoother ride. When driving over rough and rocky terrain, higher tyre pressures mean that you’ll feel every little bump along the way. On the other hand, lowering your PSI will help the tyre to absorb more of the movement that would otherwise be felt through your suspension.
Another great advantage of reducing pressure is the tyre’s ability to ‘absorb’ the shape of the terrain. This allows them to propel the vehicle forwards rather than struggling to push over the top. This also greatly increases traction while reducing the likelihood of popping a tyre.
Factors that impact how much to reduce your PSI:
The downside to decreasing your tyre pressure is that it becomes unsafe to drive quickly. With softened tyres comes increased heat build-up and an increased chance of a tyre detaching from the rim – both of which can lead to loss of control.
If you’re going to drive fast, remember to reinstate the recommended tyre pressures.
Flexible sidewalls allow you to increase your vehicle footprint without significantly reducing your PSI.
Stiff sidewalls prevent your tyres from ballooning, which means you’ll need to lower your PSI more than a vehicle with flexible sidewalls.
Lighter vehicles require a lower PSI to experience the same increased footprint. The added weight of larger vehicles helps to create downward pressure, therefore maximising the footprint.
Lowering your PSI – Rule of Thumb
While it’s difficult to provide an answer that suits every terrain, vehicle and tyres, you’ll generally need to lower your pressure more for loose surfaces like sand and mud.
For these, you can start by reducing your normal pressure by half (check your tyre placard for recommended PSI). In general, you won’t want to take it lower than 10 PSI for risk of rolling your vehicle. If necessary, you can take it down a tad lower if you get bogged however it’s highly recommended that you bring it back up as soon as possible.
For harder surfaces like rocks and uneven gravel or dirt, start with a third of your normal pressure and work your way down from there. For most 4x4, you’ll probably find that a PSI between 14-18 will do the trick, although you might need to lower it a bit further for certain terrains.
Note: If you notice your vehicle beginning to strain, bring it back up and reduce it by smaller increments until you reach a comfortable level.
And remember to check your tyre pressure regularly to ensure maximum tyre life!
Keeping your 4x4 in good shape for off-roading
If, like us, you love to get off road as much as possible, it’s important to keep your vehicle in good nick to ensure the best possible driving experience. You might also want to install a suspension upgrade kit to enhance your time off the road.
Please note: This article is a guide only. Always seek advice from a professional based on your individual circumstances prior to making any changes to vehicle setup up or configuration including any maintenance items.