UPDATED AUGUST 2020
In this article I'll detail what tyre pressures I run on my 4WD for the various road & track conditions we encounter AND how you can work out what the correct pressure is for your tyres on your rig.
If you ask a dozen road trippers what tyre pressures they run on their 4WD's, chances are you'll get a dozen different answers.
There isn't really a magic formula for tyre pressures that works for everyone because there are a lot of variables and everyone has their own experiences.
What is concerning though are the road trippers who only check their tyre pressures occasionally or, worse still, leave them at one pressure for the entire trip, despite the changing road surfaces.
Why do tyre pressures matter?
In Australia we have every conceivable road surface available to us . . . mud, sand, corrugated dirt, bull dust, gravel, sealed bitumen and even snow occasionally.
When we go on a road trip chances are we'll encounter most of these road surfaces at one time or another . . . and often in the same day!
And while doing so, our 4WD's are usually fully loaded and often towing a trailer or caravan that can weigh thousands of kilograms.
So the performance we're demanding from our tyres could not be more extreme.
Tyres designed for sealed roads have significantly different designs, construction and tread patterns than those designed for off-road - so we're compromising one way or another and most of us tend to pick something that is a good average for both.
Once you get going on your trip the one thing you can control to maximise your tyres performance, safety and wear while minimising the risk of damage or a blowout, is your tyre pressures.
And the difference is significant!
Setting your tyres at the right pressure for the job can be more effective at gaining and maintaining traction than the tread pattern itself.
Softer tyres on rougher roads are less susceptible to punctures and chipping from sharp rocks and will give you more traction over variable road and track surfaces.
But traction is only one issue . . . the bigger issue is safety.
Your life and the lives of your passengers are riding on your tyres!
A tyre blowout can be catastrophic and send you out of control either into oncoming traffic or off the side of the road.
Blowouts are often caused by tyres that are incorrectly inflated for the conditions.
Watch what happens when this Bronco towing a camper trailer gets a blowout.
Why lower tyre pressures provide better traction
It all comes down to more rubber on the road!
Reducing the pressure in your tyres has the effect of increasing the tyre's footprint or the amount of tread that comes in contact with the road or track surface.
The area where the 'rubber meets the road' gets longer and the weight of the vehicle is spread over a larger area.
When driving in sand, lower tyre pressures enable your vehicle to get up on top of the sand and 'float' across it rather than digging in.
On rocky surfaces, the lower pressure provides more flex in the tread so the tyre can grip more of the rock and conform more to the shape of the rock. This gives more traction and more 'give' in the tyre, reducing the chances of a rock penetrating the tyre.
Tips for managing your tyre pressures on road trips
1. Check tyre pressures every morning
The morning before you hit the road for the day is the best time to check and adjust your tyre pressures for the terrain you're expecting to encounter on the day.
Your tyres are cold so will already be at their lowest pressure.
Once you get going your tyres will warm up and the pressure will increase by about 4 to 6 psi.
2. Keep a tyre gauge in your glovebox or console
It only takes a minute to check your tyre pressures so keep a tyre pressure gauge handy so you can quickly check pressures anytime during the day.
You can buy some pretty fancy and expensive gauges but I use a simple $5.00 stick gauge which I keep on my sun visor and it works just fine.
The main thing is that it's accurate and gives you a consistent reading each time you use it.
3. Take a 12v air compressor and keep it accessible
Invest in your own tyre compressor so that you're able to manage your tyre pressures along the way without being dependent on a service station.
If you've lowered your tyre pressures to travel down some rough tracks then you need to be able to pump them up again when you get back to the black top.
Having your own compressor on board, where you can easily access is it the way to go.
Dropping your tyre pressures when you get to the rough stuff and re-inflating them again when you get back to the sealed road is 10 minutes well invested and a good chance for everyone to stretch their legs.
How to know what pressure your tyres should be set to
Keeping your tyres set to the right pressure for the load you're carrying and the conditions your driving through will maximise your tyre life, give you the best traction and most importantly, maximise safety.
But what is the right tyre pressure?
As a general rule, the more weight your vehicle is carrying, the higher your tyre pressures need to be.
But even 5 or 6 psi too high or too low can cause issues.
Under inflated tyres will wear more quickly on the outside of the tread and the extra flex in the tyres will cause them to heat up more and could cause a blow out.
On the other hand, over inflated tyres will wear faster in the centre of the tread and the extra pressure in the tyres makes them more prone to damage from rocks or potholes.
But you don't want to wait until your tyres are wearing too much on the outside or the inside to know they are incorrectly inflated.
There is no 'one size fits all' but you can use a simple test to establish whether you have them correctly inflated . . .
The 6 psi test for 4WD tyres*
Do this test at home before you start your road trip when you only plan to be driving on sealed roads.
- Check your tyre pressures first thing in the morning when they are cold and make sure they are inflated to the pressure recommended on your vehicles tyre placard.
- Drive for at least 30 minutes to warm them up then pull over and check all the pressures again.
- If the tyres are correctly inflated, the pressure should have increased by around 6 psi above the cold pressure.
- If the pressure increase is more than 6 psi then your tyres are under inflated. The lower pressure has caused more flex in the tyre and caused them to heat up too much - You need to add more air.
- If the pressure increase is less than 6 psi then your tyres are over inflated and you need to remove some air and test again when the tyres have cooled down (eg. the next day).
It make take you a few days of testing and adjusting to end up with your correct starting pressure for your tyre/vehicle/load combination but it's a simple way to establish the 'baseline' pressure for your 4wd.
Note - non-4wd vehicles should use 4 psi instead of 6 psi when doing the above test.
* I learned the 6 psi test from Cooper Tires
What tyre pressures do I run on my 4WD?
Having invested in a few sets of tyres over the past 25 years or so, I've reached what I've found to be the best overall tyre pressures for the driving I do.
These pressures are for my 80 Series Toyota Landcruiser which is usually fully loaded on a road trip and often towing our camper trailer.
I'm currently running Nitto Trail Grappler M/T 285/75R16 which have now done over 35,000km including crossing the Simpson Desert and a Kimberley trip (I'll do a seperate review on these soon).
These pressures are based on cold tyres, checked in the morning before we get going.
They'll increase by about 4 to 6 psi when they're warmed up after driving for a while.
You'll notice I usually run the rear tyres at a higher pressure when the vehicle is fully loaded and/or towing because they are carrying more weight than the front tyres.
I've had around half a dozen flat tyres over the years but they have always been due to sharp objects penetrating the tyre - Tek screw, rivet and a sharp rocks.
But I've never had a blowout in over 450,000 km of driving, so there's something to be said for managing your tyre pressures.
DISCLAIMER - This is a guide only - I'm not a tyre expert and I'm not advising you to run the same tyre pressures as I do. The pressures you should run will be based on your tyres, vehicle, load, terrain etc which are likely to be different to my setup.
Sealed road tyre pressures
|Front Tyre Pressure (psi):||36||40|
|Rear Tyre Pressure (psi):||36||45|
|Speed Range (kmph):||90 to 110||90 to 110|
I run 36 psi around town when my rig is mostly unloaded and increase them to 40/45 psi when I load it up for a trip. Once the tyres are warmed up on a trip they will be at around 45/50 psi.
Good unsealed road tyre pressures
|Front Tyre Pressure (psi):||32||34|
|Rear Tyre Pressure (psi):||32||36|
|Speed Range (kmph):||70 to 90||70 to 90|
Once I hit the unsealed road I'll drop the tyres to make them a little softer to improve the ride and soak up the rough patches better.
Keep in mind that it's rare to find continuous sections of high quality unsealed roads!
They usually include rougher sections, so lowering tyre pressures helps to soften the ride and reduce the wear on the tyres from occasional rocks and corrugations.
It also reduces the chances of a puncture through running over sharp rocks.
Driving fast over corrugations to 'smooth them out' with hard tyres will increase your chances of losing control and/or getting a blowout.
Let some air out and drive a bit slower and you'll be better off.
Rough unsealed road tyre pressures - corrugation, gravel, bull dust
|Front Tyre Pressure (psi):||26||26|
|Rear Tyre Pressure (psi):||26||30|
|Speed Range (kmph):||50 to 70||50 to 70|
Where the unsealed road is consistently bad or contains a considerable amount of rough sections, I'll drop down to 26 psi and reduce speed.
Tyres will be better able to soak up sharp rocks, ruts and other nasties if they are softer and you are driving slower.
Driving slower will give me more reaction time to avoid hitting large tyre shredding rocks and washouts.
Rough track tyre pressures - mud, rocks, creek crossings
|Front Tyre Pressure (psi):||22||22|
|Rear Tyre Pressure (psi):||22||24|
|Speed Range (kmph):||10 to 50||10 to 50|
This is low range 4WD type track which is probably completely unmaintained and can be any surface you can imagine.
Low and slow is the order of the day. Be especially careful when cornering as too much speed & momentum can roll a tyre off the rim.
The lower pressure will also help get more traction to climb in and out of creek beds and other obstacles.
Desert sand driving tyre pressures
|Front Tyre Pressure (psi):||20||20|
|Rear Tyre Pressure (psi):||20||22|
|Speed Range (kmph):||10 to 50||10 to 50|
With long stretches of fairly predictable sand driving like you find in the Simpson Desert, I've found that around 20psi is a good place to start.
This tyre pressure provides a good 'flotation' over the sand but the tyres are still firm enough to handle a bit of speed on smooth straight sections of track.
If the sand gets particularly soft or I'm struggling to make it up steep dune, I'll drop the tyre pressures to 16psi to get even more flotation.
Beach sand driving tyre pressures
|Front Tyre Pressure (psi):||16||16|
|Rear Tyre Pressure (psi):||16||16|
|Speed Range (kmph):||10 to 30||10 to 30|
Beach driving is risky, especially below the high tide line.
The temptation is to drive lower down the beach on the harder sand to get more traction but you also risk being swamped if you get bogged and the tide comes in.
Where possible I tend to stay as far away from the water as possible while still avoiding the seriously soft sand. This gives me more time to deal with getting stuck and an incoming tide, as well as minimising the amount of salt water on the car.
The general rule for beach and sand driving tyre pressures is 16 psi which will give you about double the amount of rubber on the sand and a lot lower pressure per square inch. This helps to float over the sand instead of digging in.
Maintaining forward momentum is a big factor in avoiding getting stuck in the sand.
Make sure that when you do decide to stop that you are on a firm stretch of sand with a clear path to drive away from.
If you get bogged or are struggling to get forward motion, lower your tyres more.
I'll even take them as low as 10 psi to get out of a really boggy situation But remember that with very low pressures comes a much higher chance of the tyre rolling off the rim so drive slow and corner gently.
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