Photo: Whether 4WD or trucks all ESS vehicles run on lowered tyre pressures on rough outback roads. Pictured here are the ESS LandCruiser and Mercedes 22 ton truck with 14 ton tri-axle trailer at the Big Red Bash in 2019.
Lucas Trihey explains what his crew does with their tyres for outback work
Lucas has been driving 4WDs, cars and trucks on gravel and sandy outback roads since the 80s. He has worked on everything from the first Australian Geographic expedition to the remote Coongie Lakes in 1986, to supporting desert trekkers across the Simpson to leading the team that over seven years has set up the legendary Big Red Bash musical concert 35km west of Birdsville.
In my early outback driving I was lucky enough to meet Adam Plate from the Pink Roadhouse at Oodnadatta. Adam had witnessed and repaired thousands and thousands of punctured and damaged tyres from the rough South Australian outback roads. From Adam I learned that the best preventative against tyre damage is to run pressures significantly lower that highway pressures.
Adam told me that a softer tyre will ride over a sharp rock rather than battering into it at high pressure with more chance of damaging the tyre structure via repeated small cuts and tears that will eventually lead to a failure.
What we look for when deflating is an obvious bulge to the tyre that shows us that the tyre will be a little more spongy to absorb the shocks of a rough road surface and the occasional sharp-edge rocks laying on the surface.
On our event 4WDs and smaller cars we usually decrease pressure to about 75% or 80% of highway pressures. On our trucks we deflate to about 55% of highway pressures.
The tyres on a lightly laden vehicle will need a little more deflation to achieve the desired bulge compared to a heavily laden vehicle.
4WDs AND CARS
Typically we’ll deflate my event LandCruiser (a dual cab 70-series with a couple of passengers and about 500 kilograms in the back) to 25F and 30R to get the bulge we want It’s currently on Goodyear Wranglers – a medium to heavily structured tyre. Our single cab Triton Ute will be deflated to 18F and 25R if not heavily laden. We have a Nissan X-Trail (with highway tyres) in the crew convoy and it’s usually at about 18F and 20R for the desired bulge.
We’ve always run our event trucks at far lower than highway pressures and a few years ago met a double road train driver at the end of the sealed road (110km west of Windorah). He’d just delivered 45 tons of fencing materials to a station further west and he told me his company’s guideline is “50% pressures on the gravel mate”.
Our trucks often carry loads onto on soft, sandy surfaces including the lake bed for the Big Red Bash and the sand dunes of the Uluru and Burke and Wills treks.
We run a few large and medium trucks from NSW to the Bash and these tend to run at 50% to 60% of highway pressures to get the desired bulge. My Mercedes Heavy Rigid truck is a bogie drive, 6.5m tray, rigid truck with a rear loading crane that weighs 12T empty and is typically around 20T when loaded for the Bash. It pulls a 6m tri-axle trailer with super-single tyres. It runs 55psi all around once on the gravel roads (recommended highway pressures are about 110psi).
We run our semi trailers at about 60% all round (prime mover and trailer). Our medium rigid single-axle-drive pantechs tend to run at 60% of highway pressures all around on the gravel.
On the return trips we happily leave the pressures low as we poke back along a sealed road to the next servo where we re-inflate. But for the now mostly-empty trucks we’ve often run them back to the Blue Mountains at 55% and the tyres are standing up tall again and we’ve seen no obvious signs of unusual wear or seen any issue with handling or heat.
Since the 2018 Bash we’ve run tyre monitors on our 4WDs and the HR Mercedes truck so we can monitor pressures and temperatures from the driver’s seat. These have validated our pressure decisions – and we’ve seen that running lower pressures on the gravel hasn’t led to over-heating.
Monitors also alert you to a rapid deflation so you can stop before the now-flat tyre is destroyed. One destroyed 4WD tyre is roughly the cost of a set of tyre monitors. We use SAFETY DAVE external units but there are many brands.
LOW PRESSURES AND SPEED
What we’ve seen via our tyre monitors is that lower pressures on 4WDs and trucks seem to be fine for the maximum speeds we feel safe at on gravel roads. Once back on the bitumen we usually inflate back to the manufacturer’s recommended pressures. However we often run our own 4WDs and trucks on lower pressures on sealed roads to get back to a nice fast compressor at slightly lower than normal speeds without ill effects. Tyre monitors are really good in these situations because the driver can watch the temps and make sure nothing too silly is happening.
OUR RECORD WITH TYRE DAMAGE
Since adopting low tyre pressures on our crew vehicles we’ve seen a sharp decline in blow outs and punctures. In my early outback driving days it wasn’t unusual to have multiple punctures and more than one blowout on some of the rougher SA outback roads.
These days we still get an occasional flat tyre but nearly always these are caused from picking up a screw or sharp piece of wire at the town tip or council yard rather than from a high-speed blow out.
At the 2018 Bash with four crew or event trucks and a dozen 4WDs/SUVs we got two slow leaks on the trucks and one slow leak on a SUV. None of the 4WDs had tyre damage. At the 2019 Bash with four event/crew trucks and a dozen 4WDs/SUVs we had one tyre failure on a sponsored Amarok (a direct hit on a very large, sharp rock near Innamincka). There was no tyre damage on the trucks or other vehicles.
HOW MANY SPARES DO WE CARRY?
A search of the online 4WD and outback forums will see lots of recommendations that you need “two spares” for outback driving. Taking two spares isn’t a bad idea but remember that a spare wheel is a very heavy item. For my own and our convoy vehicles we only ever carry one spare now – simply because we hardly ever get tyre damage. If I had a vehicle with tyres down to the last 15% of tread I’d think about taking two spares but for a good tyre, not too old, we only bother with one for most trips.
TIME TO REPLACE OLD TYRES?
We usually replace older tyres BEFORE a big trip. We believe it’s a false economy to try and eke out every last kilometre from an old tyre on an outback trip. Have good tyres at the start and you’ll be less likely to be forced to get a non-matching or inferior tyre from a remote outback roadhouse. You’ll also be less likely to get flats from dropped nails or screws.
LOW PROFILE TYRES ARE A BIT SPECIAL
Low profile tyres are a bit challenging on rough roads. It isn’t possible to run them at the low pressures we usually like because there simply isn’t the same amount of buffer between the outer tyre surface and the rim. If we hit a medium sized rock with low pressures on a low profile tyre it can do rim damage and possibly result in a pinch flat. If we have to take a low profile tyre on these roads we don’t run at our normal low pressures and we accept that we’ll probably see more damage to such tyres than we are happy with. We also drive more slowly and try our hardest to avoid rocks. We generally upgrade low profile tyres to bigger more conventional profiles as soon as we can. We currently have a 5.5m flat top car trailer that came with low profile tyres that we took to the 2019 Bash and we’ll be upgrading as soon as we can.
SUMMARY OF TYRE CARE FOR ROUGH GRAVEL ROADS
- Our 4WDs and cars run at 75% to 80% of highway pressures.
- Our large trucks run at 50% to 60% of highway pressures.
- Tyre monitors are useful and help you monitor pressures and temps. Monitors also warn you of a rapid deflation so you can stop before a very low pressure tyre is destroyed.
- We usually carry only one spare unless we have older/more worn tyres in the mix.
- Replace old or worn tyres before your next outback trip.
- Low profile tyres aren’t great in the outback. But with slower speeds and more care we get by.
WHAT SHOULD YOU DO?
We’ve explained what we do with our crew vehicles but we because everyone’s needs and situation is different we make no hard recommendations – do your research and make your own decisions.