tyre pressure recommendation - outback way

Supporting the local tyre sellers?

We've just done a trip through the Simpson, Ghan to Alice etc and we found that there are a great variety of opinions out there.

Some say keep them tight (one guy recommended 40psi) on stones to protect the firewall.

Others say run them soft to keep the tyre flexible over the stones.

We went with softer, even down to 20psi on stoney sections (because I forgot to put them up at one stage) and didn't have any problems. But I'm sure there are others who keep them tighter and have no problems.

Dion
My Camp Gear

This is one of these stories that will get you a thousand different answers. I always prefer lower tyre pressures, the old balloon trick.
Half inflate a party balloon, then pinch it, it will not burst. Now inflate a balloon fully and try the same and it will burst.
The same works with car tyre pressures. A soft tyre will flex over the rough surface, a full pressure tyre will have no give and you will suffer tyre damage. Other so called experts will not agree, but it was always worked for me out bush.

Cheers

Stephen

This came up about a month ago.

I run LC80 and now LC100 with BFG AT at 40-42 psi on highway....both tar and dirt. Many thousands of clicks on unsealed. 3rd set. Nil punctures.

Tread section is thick, more plies. Sidewalls are thin, less plies.

Works for me.

Used to do it, keep the tyre pressures up.
Now drop the tyre pressures about 5 to 10 psi for the dirt.

The milk doesn't turn to cream as quick on the corrugations, and the tins of beer don't rub through as quick either :o)
So it must be better for me too.

Well Lex, after many years of driving on sharp rocks (we will leave the gidgee stakes out of this and stick to sharp rocks) I have found lowering tyre pressures reducers punctures quite a lot.

The fitter would pump the things to 50psi+ and I would promptly let them down to 35psi and that's having a 1t hiab in the back and carrying loads.

I used to get up him about the pressure because my back didn't like it at all.

Then I reminded him that our utes wear the tires to the wire with very few punctures, the other utes they would have to trough the tyres out when they were 70% worn as they would constantly puncture.

Before people get up me about running around on bald tyres these vehicles are off-road only.

22 cents worth (inflation)

I want Willem's opinion on this, mind you he might inflate his new tyres to zero and by the look of the photos there may be no difference ...

In my opinion this letting air out of your tyres as soon as you get on rough roads is a bit over done!........I have just finished a trip,7000kms to Mount Augustus, Millstream, Karijini, (on some real bone shaking roads) with My LC100 series and off road van, ran the tyres on both the LC and Van at 40psi all the time, just adjusted my speed to suit the road, no problems..

I have done all those roads without punctures towing the van.
Have always reduced tyre pressures to reduce stress on the shocks and the vehicle and van. Also found that in steep rocky terrain it helps the tyres to grip as well. So works for me.

Having read the replies to this very interesting topic, I am totally confused - I don't know what to do now!

Million dollar question, speed and tyre pressures go hand in hand, have a yarn to Neville at Over The Range tyres & repairs next to the Imintji roadhouse on the GRR he sees a few busted up tyres in the season and will probably never see you again to sell you another one. If you want to preserve yourself, tyres, your vehicle and the road, then lower your tyre pressures 8-12 psi AND your speed. Hard tyre pressures will not conform to the shape of on road obstacles as well as reduced ones. IE rocks can be punched through the tyres tread rendering them unfixable, logic behind this is the tyres steel belts are unable to flex if the pressures and speed are too great, where they are more flexible if pressures are lessened and less likely to be penetrated. Happy trails.

I am one for the reduced pressures over the stoney stuff but you MUST reduce the speed as well or risk sidewall damage through heat buildup.

Why people have to belt along at 80 to 100 km/h all the time on outback roads beats me!

Muddy

That suggestion by Outback Way may not be as bad as it sounds. It says "at or near highway pressures'. It does not say don't reduce them.

I think the whole thing revolves around what you are bringing them down from. Are you at factory pressures to start with or are you way above them?

I just said in thread 61831 that I have had good results both on and off road with factory pressures in stock size tyres. That is 25 psi front at all times and 25 to 30 rear depending on load.

I do not reduce them below those pressures on Outback roads but I do reduce speed considerably. If I was to drop them, I doubt if I could do it by any more than two to three PSI without getting too low. If I did do that I would say I would still fall into the "at or near highway pressures" category.

Brian

really, this is just pretty basic physics, Have a look at what actually happens to tyres when you let the pressure down, not what you think happens. It has almost nothing to do with bulging sidewalls. Sit your vehicle on level hard (it has to be hard, so you can see what happens) road with the tyres at high pressure. Note the length of the footprint of the tyre, that is , the actual area in contact with the road. There isn't really much contact are, so all that weight is concentrated onto a small area resulting in a great deal of pressure anywhere on that footprint. Now let the tyres down to 25 or less. You will find that you get a much bigger footprint. This means that the pressure on any given impact point is much less so the chances of the object being driven through the tyre are much reduced. Especially note the direction of the increase in footprint. It isn't gained by the tyre bulging sideways very much, it is gained by a big increase in the length of the tyre running along the ground. Increased danger of staking through the sidewalls by reducing pressure is very minimal while the reduction of the chances of staking as a result of reducing impact pressure across the whole footprint is considerable. Lets face it, punctures are a lottery, so you play the numbers. While sidestaking is always a possibility, the chances of a puncture directly through the tread are much greater. You can always be unlucky, but the odds favour reducing pressure.
Remember those skinny old landrover tyres that could still get vehicles over terrain that defeated fat tyres? Those skinny tyres on low pressure had a much longer footprint, hence less pressure on the ground. Same principle. I don't think it has much to do with increased flex at lower pressures, it's a question of the amount of pressure on a given point.
As everyone notes, the downside of course is that lower pressure tyres must be driven more slowly. This isn't, in the main, because of heat build up from the sideways flexing of the walls of the tyre, most of the heat build up is from the longitudinal flexing resulting from the big flat area on the bottom of the tyre as it rotates.

Lex M,

As you can see from the replies so far this is a subject you will not get a consistent opinion on so it's one you're going to have to work out for yourself.

I made my mind up by doing a couple of tests. Get yourself a nice sharp stake or a sharp rock, they're the ones that penetrate sidewalls and remember that when pressures are down the sidewall is very exposed and, when it does come in contact with an object will be supporting a fair percentage of say a 2 tonne vehicle.

Get yourself a balloon, put 20 psi of air in it place it over your sharp object put a great deal of weight on it and see what happens. The test that Coopers do is flawed and does not replicate the true situation.

Then get yourself a case and run your fingers on either side of the roll near where the tread ends and feel how thick it is. Remember when you air down that roll is exposed. There's no tread or steel belt to help against penetration.

You get penetration there and your tyre is cactus it is illegal to repair in that area.

So you've just blown a $300 tyre and it's going to cost much more than that to replace in the outback, I know.

Talk to the locals and find out what the pressure are that they run. Also talk to the tyre guys in those outback towns and get their views.

Newman Tyres, Newman would be a good one to start with they are in the middle of stone country and service all of the mine vehicles who are operating in some of the harshest country in Australia.

I did all of these things because I got sick of following the norm and having to replace tyres. I use to air down, not any more and haven't had a puncture since.

The advice provided by that website is sound as is the advice given by Steve from Top End Tours. He provides tour services and he doesn't want to be replacing tyres all of the time, and it has nothing to do with luck.