Weird advice.

maybe you need to update your photo, the 19ft Bushtracker looks like a Tvan to me. I am as bad kept my Tvan and now have a 19 Ft Sunland. good safe travels

When and where did this rule of thumb come into place dropping 4 to 6psi never heard about it. Was it in a 4wd action mag or something.

Batts it’s been the standard for over 25 years in our experience.

My advice from an experienced tour operator was more percentages. 10-15 per cent was his rule of thumb.
Which, if you running around 40psi as I do, equates to 4-6psi.
That's just on gravel and good dirt.
Corrugations and sand it's much lower. 
Advice has stood me in good stead.

Cheers

But where does it come from David is all I'm asking who told you there is a standard practice out there that we all should know about ? I've traveled around this country for around 35yrs and nobody has ever told me about this particular standard to follow.
We made our own choice to air down if we wanted to on slower 4wd tracks but not for general gravel roads we drive to suit.

I learnt it in the defence force. We drop our 35psi tyres to 25.

Thanks Ivan you learned about it from people with experience.

Learnt so much that you dont see anywhere else. Stuff that has saved me countless times

Having been in the military, underground mining, farming and having been an adventurer all my life and being a bit scientific to boot ....I reckon not only have I learnt from people with experience - I am one of those with experience. Dropping tyre pressure is a basic necessity - quite often.

Trouble is there are many things to consider - there is no black and white rule. Quite simply unless you understand all the parameters (tyre size, type, brand, side wall flexibility, road conditions, driving style, conditions of road {eg gravel, sharp sandstone, mulga stakes, mud, sand, ironstone gravel, wet butumen, wet gravel, wet mud, wet sand etc etc} vehicle, capability, diff locks, traction, power, driving style, experience, load, potential for spin, potential for punctures, fatigue, schedule... need I go on - many people are only guessing and those that ignore how beneficial adjusting pressure for optimal tyre life, traction and safety really miss out on the opportunities to "know thy self and thy vehicle". My point?

1/ Dont knock it till you try it.
2/ Each to their own. You will survive quite well with what you already know!
3/ You are always learning unless you close your mind.
4/ Don't assume other people are not intelligent... maybe we can all learn from the most unassuming sources!
5/ The loudest voices are not necessarily the wisest.
6/ Magazines, media and social media "experts" usually have a sponsor, agenda or bias and will promote those regardless of how it works for individuals...

Just enjoy your vehicle and adventures and endeavour to get home safely.

Here endeth the lesson from Kerry. :)
Dave.

Thanks Kenny I also learned from more experienced people I traveled with in my early 20's they never claimed there was a rule of thumb or standard they learn't from. They learned from others, experimented with different tyre pressures and lowered speeds to suit. Some of the people with light weight Suzuki's would lower their pressure more than others with heavier cruiser or patrols but that can be the opposite way around for beach driving we learn as we go.

Nope not correct either. When we air down on corrugate roads we do so, to enable the vehicle to ride better over the corrugations at higher speed. We often drop pressures somewhere between 32 - 28 psi and will drive anywhere between 60-100km/hr - sometimes the conditions will predicate a lower pressure required. Usually lower is only required if very sandy, or churning through rocky creek beds etc with a trailer in tow. Obviously not that fast for a creek bed but on open roads you can easily drive at 80-100 with lowered tyre pressures depending on the nature of the road. We experiment and drive to conditions and adjust tyre pressures accordingly. After more than 25 years of outback driving and rarely any tyre problems this just becomes second nature and you get a feel for what pressures suit your rig and yourself. In fact, at slow speeds corrugations can feel much worse than if you just punch up the speed a little more and the vehicle "rides over the ridges". Corrugations occur in both sandy country and rocky tracks and the same concept of drop tyre pressure to drive faster applies. With experience this becomes second nature.

Good advice Briste less air less speed.
Also it doesn't always mean people want to drive faster if they don't air down their vehicle and suspension setup makes a big difference. I had a GQ patrol dual cab coil springs all round extended chassis nearly 20 foot long 285 tyres adjustable shocks. Most of the time I just tweeked the shocks and it absorbed the bumps and the larger tyres with 38psi already had lots of sidewall flex as larger tyre tend to have. Same sort of thing with a 1980 60ser cruiser I had OME suspension it was the best leaf sping ride comfortable but stable. My current 2007 BT50 is crap but I haven't set it up for off road use it's not worth spending the money on it.

Unless I am missing something Peter, that graph shows no relationship between tyre pressure vs speed.

It does show a relationship between tyre pressure and maximum load, for 3 types of road scenarios. Sand, at low speed, off-road, at medium speed and highway, at high speed.

The appropriate pressure for a tyre is dependent on weight.
If you are driving at the pressures (and weights) indicated anywhere along the yellow line, you are limited to 20kph to avoid over heating. That is a pressure related speed restriction.
Cheers,
Peter
OKA196 motorhome

ps... the chart does not show "maximum load" for a particular pressure, it shows the "appropriate" pressure for specific loads (@ 3 maximum speeds). That is a none too subtle difference.

Agree with Peter, you need to be careful when you lower your tyre pressures, and be guided by the weight the tyres are supporting. Not only the weight the tyre is supporting, but also its construction.

An LT tyre with a stronger side wall is less likely to fail running at a lower pressure than a “highway” tyre. This doesn’t mean you can safely run very low pressures with an LT tyre, you still need to be careful when heavily loaded.

There is no “one size fits all”.

Macca.

Dunno, I had mine fitted with the white lettering on the inside of wheel.

.
Wouldn't that make the vehicle go backwards when in a forward gear??