View Full Version : Getting 4WD Tyre Pressure Right

11-04-18, 10:32 AM

Iíve long said that the single best value for money modification you can make to your 4WD that will get you further off-road than anything else, hands down, is tyre pressures. Adjusting air pressure in your tyres can cost you nothing, yet it is the single best thing you can do to your rig across the board to increase performance.

Adjusting your tyre pressures increases or decreases your tyres footprint or surface area in contact with the ground. This offers lesser or greater resistance (grip) and alters your tyres reaction to the terrain over which youíre travelling.

Starting with the blacktop, I would hazard a guess that I keep an eye on my road pressures at the very least once a month but probably more frequently. A few years back I found on my GU that by increasing my road pressures well above what I had been running them at, I was able to save a litre of diesel per 100kms travelled. Just by getting my on-road pressures correct. Itís like Iím making money now as a result!


As soon as I leave the black top and venture on to any other style of terrain for a prolonged distance, Iím instantly thinking pressures. From black top itís very common to hit high speed gravel (my second favourite terrain to beach driving by the way) and to rack up some big distances on said terrain. Road pressures suck on gravel; itís uncomfortable for you and your passengers and contributes towards the creation of corrugations. Dropping your pressures, as well as your speed, smooths out the ride, makes it safer. High pressures and gravel combined with speed equals a lack of gripÖ. hold on! As a very general rule of thumb, for high speed gravel Iíll drop my tyres to around 28PSI.

I mentioned corrugations and on some lengths of track they can be utterly diabolical. Head out towards Steep Point, the most westerly point on mainland Australia and youíll see what I mean. These tracks still allow you to travel with speed but high pressures will just about rattle your rig to pieces. In these conditions Ill drop my pressures into the low 20 PSI range and then adjust my speed to find a comfortable maximum.


Next up letís think about low range conditions, steeps, rocks, ruts, mud and anything else that causes you to engage the stubby lever. Itís in these conditions that traction is key. Low pressures increase the ground surface area that your tyres are in contact with. More contact area, greater possible traction. Also, lower pressures enable your tyres to mould around obstacles, again improving contact, reducing the risk of tyre damage and increasing traction. My go-to starting point for anything low range is 18 PSI.

Then we have sand; perhaps the most critical location for correct tyre pressures. As a rule of thumb, as soon as I hit a beach, I drop my tyres to 15 PSI. I then perform a very quick test to see if Iím in the ball park; simply build speed then disengage your gears, stop accelerating and let your 4WD coast to a stop. If your pressure is correct your vehicle will come to a slow and gradual stop. If your pressures are too high, you will stop suddenly as the tyres dig in. This is a fantastic rule to work by and I urge you to give it a crack. Remember the lower your pressures, the slower you must drive and avoid sharp turns as you run the risk of busting a tyre bead, which is a real pain in the backside.

Learn to master this art and I assure you, any terrain will be looked upon differently; youíll drive more efficiently, in more comfort, with greater traction and further, simply thanks to the best value modification you can make, tyre pressures.

By Graham Cahill


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