Recomended <span class="highlight">Tyre</span> <span class="highlight">Pressures</span>

Sorry, I should have mentioned that.

It is a NJ Pajero, Maxxis MA-751, loaded with a small camper trailer.

Looking at cutting across the Plenty Hwy from Alice Springs to Boulia then down to Birdsville.

Cheers

Usually between 20 and 25 on my cruiser on heavy corrugations. Lower pressures do mean you have to drop the speed. Many drivers travel too fast with too high pressures and bust things. Too fast on low tyre pressures will cause problems too, like overheating the tyres. I only go below 20 on sand.

Expect you will take an air compressor and you can experiment a bit to see what suits you.

Flynnie

22psi...............................................................................

Been on the Plenty six times and carry a good ton in my Cruiser, run the BFG'S at 50 psi rear 40 front and sit on between 60/70 kms per hr when i can a lot of the time down to 40 kms per hour. No blow outs and haven't brocken anything yet. Also tow an off road Pop Top. Speed will kill everything and your wallet. There is no fuel at Tobermory anymore so will pay to fill up at Jervois Station.

Hey Matt L

I agree totally, It is not rocket science.

Richard
The roads that you are intending to drive are usually good roads to drive and if you work on the 20% rule, or like Voxson has stated, will will be on the mark.


Stephen

Richard,
Just read the extra bit about the Plenty highway.

Like all dirt roads it will depend on grading and how soft the road is after rain.

Hi John

I also know about the 4 PSI rule, but one part that I have often read stands out and it often doesnt get related in conversations. I was curious as to what your opinion of it was if you have heard about it...

Most publications of the 4 PSI rule state that 4 PSI is for CAR tyres BUT to use 6 PSI for larger 4WD tyres. Any comment as to whether you believe it should be 4 or 6 PSI?

And when is a tyre large enough to be considered for the 6 PSI Rule (ie: does a standard 4WD tyre mean 6 PSI or it is only if the tyre size is increased as often it is for more serious 4WDing, larger Muddies, competition stuff etc) - cheers....

Hi,

I look on the 4psi rule as a guide only, as too many other factors interfere with it to take it too literally. (For those not familiar with this "rule" - one school of thought that's fairly widely held is that tyre pressures should be set so that the heating caused by the flexing of a tyre will result in a pressure rise of 4psi - measure pressure before driving and again after 50 km or so when it's warmed up - if the pressure's gone up by less than 4 psi, let some more air out, if more than 4psi put some in.)

In practice, the tyres on the sunny side get much hotter than those on the shady side. In practice the loading is different on each wheel. In practice most gauges aren't consistent enough or accurate enough to allow us to be too fussy. Then there's the matter raised by PradOz - 4psi or 6psi? It really isn't possible to use the rule rigidly. I think the 4 v's 6 psi debate arises from the fact that larger tyres will often be running at higher pressures, so 6psi represents the same percentage pressure (hence temperature) change as 4psi in a smaller tyre. I generally consider percent changes rather than absolutes, and in rough going check the temperature of shocks and tyres periodically as a guide to which one's being worked too hard. Working too hard also points to too much speed.

Apart from comfort, dropping tyre pressures has the big advantage of creating a bigger footprint and better traction. Not a recommendation, but to indicate practicable ranges of pressures, with a loaded Troopy on bitumen I usually run about 30/35 psi with fat tyres (more with narrow splits), drop to 25/28 on good gravel and down below 20 on loose sand. As said - that's not a recommendation and the optimum for other vehicles, loading, tyres, drivers etc.... will be different.

Very important to slow down at reduced pressures.

John

I find the 4 psi rule a load of rubbish. Who in their right mind would stop every 50km to check tyre pressures? In reality we constantly change speed, drive on different surfaces in sun & shade, dry, wet & even snow. You would have to have an automated onboard self inflation system to make it work.
Better to use history as a guide to what works for different vehicles & ajust to your own circumstances. This link is a good start angled at minimising punctures on outback roads but the recommended pressures would give a reasonable ride on corrugations too. Pressure guide.

The 4psi rule doesnt require you to stop EVERY 50km. I believe the recommendation is a stop after about 100km (from all the bits i have read on the 4psi rule). If the pressures were right at stop 1 you check them only once. If it required adjustment after 1st stop you may want to check them again, up to the individual and their experience, confidence etc. Most people stop regularly for breaks so its not a drama to quickly check the tyres is it? When I tow i always walk around and check everything at every stop i do just in case something has come adrift or requires attention. Better than just getting out and walking off missing something obvious that could prevent a problem later. I think the 4psi rule is a good way to start looking at your pressures and when you are more comfortable with your setup you wouldnt need to check them at each stop. By doing th e4psi bit you can check your air guage and know whats happening in your tyres too. All comes down to experience and personal circumstances....

Crackles - I wasn't suggesting stopping every 50km to check tyre pressures, simply trying to express in a sentence or 2 the essence of the the "rule", which is to aim for a 4psi increase in pressure once the tyres have warmed up. The 50 km figure is a reasonable time for the tyres to reach a "warmed up" state. You quickly learn from experience the pressures that will produce the desired effect. The effect itself is very variable for the reasons you give, and others reasons too, especially loading. I don't use the rule myself - nor do I use rude and abrasive language like "load of rubbish", "Who in their right mind..."

Your link to the Pink Roadhouse recommendations is a good one and distills a lot of outback experience into a small space.

John

I understand how the principle is theoretically supposed to work but unless someone is driving at a constant speed in the same conditions, the variation in pressure will always change. So to make the rule work you would need to stop & check everytime environmental influences changed. There are many anomalies to the rule as well like if you were to drive on a tar road in the wet at 100kph with 20 psi (something no one recommends) the water would cool the tyres & be lucky to get a 2 psi rise.
As I was speaking in general terms John there was nothing rude or abrasive meant simply colloquial terms that I felt best describe the 4 psi rule.
Cheers Craig............

I have to agree with Stephen on dropping to lower pressures. having high pressures on badly corrugated roads is just lunacy. Everything just shakes to pieces and in time, things will break, especially shockers which just over heat and the oil will boil inside them unless you buy the super expensive competition type.

Good post Stephen

Phil

Nice photos , is the tryes on the Prado and Troopy at 18 psi ?

Hi Matt
On my Prado, I was running 22psi. The Troopy was complaining how bad it was and everything was shaking to pieces in his vehicle and was running 40psi. He dropped his pressure and could not believe the difference.

The Connie Sue corrugations were for only about 40 kilometres, where as the Anne Beadell were over 800 kilometres and worse.

Cheers

Stephen