Oodnadatta track rough on tyres?

2luxes

Well-Known Member
#22
I would think this is more about the driver than the car, tires or pressure , some drivers can not handle a car when slipping sideways because they never learnt how and / or never masted how ( maybe an indictment of driver education in Australia), personally I am happy to drive at 100+ on dirt roads and happy to drive a car sideways on dirt or bitumen.
Can you tell all of us how to drive a car at 100+ when it is sliding sideways after having lost traction on a dirt road and either the front or rear wheels or both hit something like a hole, a deep patch of sand or a rock and stop sliding while the rest of the car wants to keep going?

The old Westmead speedway in Sydney had a smooth dirt surface that often developed a few rough spots just like the Sydney Showground and roads like the Oodnadatta track. I saw champion driver Jeff Freeman drive many times but it all ended when his car's rear wheels hit a rut while sliding sideways.
This is the type of accident that destroys so many cars and kills drivers and passengers each year on major Outback roads.

The situation has become so serious that about five years ago Vic Widman https://www.google.com/search?q=vic.....69i57j0l4.9871j0j7&sourceid=chrome&ie=UTF-8 wrote a story for "ON the Road" magazine about the need for driver training for good dirt roads. They can easily lull many drivers into a false sense of security. There is plenty of training available for rough mountain tracks but they are a completly different story. They occasionally cause a car to tip over but serious injuries are rare because there is next to no speed involved.
 

mikehzz

Well-Known Member
#23
I would never drive at that speed on unsealed roads, particularly in sandy desert conditions. I rarely exceed 60 and are often well below that. The most common accident in the Outback is a rollover and they have killed many people. There are are endless changes to the road surface that, if entered at high speeds, can throw the car all over the place.

A major point when it comes to the way a car handles is the tyre slip angles. Few owners even know they exist. They are the angle formed between where the distorted tyre is pointing in a corner and where the wheel is pointing. They can be altered by changing tyre pressures or weight distribution from front to rear or side to side. They decide whether the front end runs out wider in a corner or sudden swerve or the rear end slides out and the car tries to spin around. Manufacturers set cars up so the front runs wider (understeer) because it is easier for the average driver to control. Oversteer is when the rear end goes first and very few drivers can confidently control that. To do this the front angle is always higher than the rear.

Long flat and fairly smooth unsealed roads like the Oodnadatta or Birdsville Tracks often contain small sandy patches, holes, small patches of rocks or corrugations, washouts and many other obsticles that can come up suddenly and cause a driver to brake or swerve hard. That is when far too many drivers find out the hard way that changes to the car design or manufacturer's instructions like non standard tyre sizes, the pressures they think are best, their incorrect weight distribution, their stiffened rear suspension and so on can leave the car very screwed up and their hair standing on its end.

Most of these situations can be eliminated by keeping the speed well down.
The secret to your success is driving slow. You can run whatever pressure you like out there if your speed is down. I had a long discussion with Adam Plate who used to run the Oodnadatta Roadhouse and had seen more damaged and flat tyres than almost anyone. He was pretty adamant that tyre pressures should be lowered and had a printed guide sheet as a public service. The guy in Birdsville had the same opinion which made 2 out of 2 people I talked with. Those guys rarely see a tar road so not a problem having to constantly air up or down.

I don't really think there's a right or wrong, especially if you keep your speed well down. However, the car doesn't rattle nearly as much with less air in the tyres which suits me better.
 

2luxes

Well-Known Member
#24
He was pretty adamant that tyre pressures should be lowered and had a printed guide sheet as a public service. The guy in Birdsville had the same opinion which made 2 out of 2 people I talked with.
A lot depends on what tyres you are using. In my case the tyres on the Hilux that I have been using since 2007 are standard specification 205 x 16 size in both LT and AT. The only difference between the two is the tread patten, the rest of them is identical. I bought a new but second hand set of HTs for next to nothing on Ebay and alternated them with the LTs on Nissan Navara wheels until both of them got too old. I now use AT permanently.

The handbook pressures for the LT and AT are 25 psi front at all times regardless of load and 25 to 34 rear depending on load. It also says for the purpose of setting pressures, the car is considered to be empty when carrying two people and up to one hundred kilos of luggage. Goodyear told me that each one psi increase at the rear will support 70 kg. The car is always 200 kg under GVM for desert driving and even lower in mountains along the Great Dividing Range so I use 31 at the rear for deserts.

Those pressures are fairly low and I initally doubted they would work on the street without wearing the outside edges faster than the centres but when you stop and think about it, both the suspension and tyres have gone through millions of dollars worth of research and development with both the car and tyre manufacturer working together. They have been designed to work together both on and off road. That is what owners, particularly those living in rural areas, expect when they buy the car. If the car manufacturer wanted drivers to change pressures for different road surfaces, the pressures would be listed in the handbook and a hand pump or compressor plus a pressure gauge would be standard equipment on the car.

I suppose you could say that when I am driving on major desert roads or remote tracks, I am running on low pressures. Many people reduce their pressures and they are still higher than mine.
 

mikehzz

Well-Known Member
#25
I tend to run handbook pressures as well. They're always well under what tends to be normal from tyre shops these days. If you're running mid 20's then you're running around the pressure recommended by Adam.
 

discomatt

Well-Known Member
#26
All manufacturers would work with each other and find the best compromise to cover all conditions, that doesn't mean you can't or shouldn't change pressures to more suit different conditions
 

2luxes

Well-Known Member
#27
All manufacturers would work with each other and find the best compromise to cover all conditions, that doesn't mean you can't or shouldn't change pressures to more suit different conditions
Providing you know what you are doing and unfortunately the vast majority of drivers don't. Toyota's recommended 25 psi at all times on the front of my single cab will result in a certain slip angle and they don't want it to change. Changing pressures will change it.

There is a lot more weight on the front wheels when the car is empty so even though the presssures are the same at each end, the front slip angle is higher than the rear and the car will understeer. When weight is added to the tray and is correctly distributed, it will cause more weight to be directed to the outside rear wheel in corners. This will start increasing the rear slip angle. By the time you get the maximum load on it, the rear angle will be higher than the front and the car will now oversteer and slide its rear end out in corners. That can be disasterous for most drivers on good sealed roads let alone at high speed on dirt with rough spots here and there.

This is why the rear pressures must be increased in proportion to the load because increasing pressures decreases the slip angle. If done correctly in accordance with the car manufacturer's instructions, the factory designed front to rear slip angle will be maintained and the car will once again understeer.

When an owner who has no understanding of suspension design starts changing tyre sizes and uses whatever pressures he/she thinks is best, who knows what the car is going to do.
 

2luxes

Well-Known Member
#28
They're always well under what tends to be normal from tyre shops these days.
My car had 40 psi at both ends when I bought it at an action. It was stock standard with no accessories and a Toyota aluminium tray. I reduced them to 25 front and rear as per the handbook and booked it in for a wheel alignment at a tyre service. The bloke immediately increased them to 40.

I took it home and rang Goodyear and was told to use Toyota's pressures at all times both on and off road and never reduce them. He also said if I decide to increase them then do not go any higher than 4 psi. I don't know where these tyre services get their information from.

I talked to that Goodyear tyre engineer for twenty minutes. He even told me about an Outback tyre testing project that he was involved in where the object was to destroy the tyres.

Another part of the conversation was the 4 psi rule that is often mentioned on the net. He said Goodyear has carried out extensive testing and found there are far too many variables for it to be accurate so forget about it.
 

billolga

4x4 Earth Contributer
#29
My car had 40 psi at both ends when I bought it at an action. It was stock standard with no accessories and a Toyota aluminium tray. I reduced them to 25 front and rear as per the handbook and booked it in for a wheel alignment at a tyre service. The bloke immediately increased them to 40.

I took it home and rang Goodyear and was told to use Toyota's pressures at all times both on and off road and never reduce them. He also said if I decide to increase them then do not go any higher than 4 psi. I don't know where these tyre services get their information from.

I talked to that Goodyear tyre engineer for twenty minutes. He even told me about an Outback tyre testing project that he was involved in where the object was to destroy the tyres.

Another part of the conversation was the 4 psi rule that is often mentioned on the net. He said Goodyear has carried out extensive testing and found there are far too many variables for it to be accurate so forget about it.
Go to Errington Hole Beach near Robe & see how you go (Tell me when you do as I would like to get a video).
Last time I was there we were using around 10 psi.
 

2luxes

Well-Known Member
#30
Go to Errington Hole Beach near Robe & see how you go (Tell me when you do as I would like to get a video).
Last time I was there we were using around 10 psi.

I have no interest in beach driving. Three months of it all day every day about 45 years ago with the RAAF cured me of it for life.

If you need 10 psi on beaches then use it. In amongst hundreds of old books and magazines in my shed is an old 1950s American book that has a photo of about ten stripped down 1928 to 1931 2wd Model A Fords driving all over big sand dunes. Their tyres from memory were 8.20 x 16 running on about 6 psi.

This discussion is about high speeds and accidents on major unsealed desert roads. Beaches are not in that category.
 

discomatt

Well-Known Member
#32
Not a equal comparison, someone on a speedway track driving a car to its limits to the point where you turn in well before the corner and drive it through sideways is nothing like driving a straight road well under the cars limit. How do I know this, um well because I have driven speedway and trust me the Ood at 100 is a lot slower.
Come up to a corner, slow down, look well ahead and if there are changes in the road slow down, if you are unlucky enough to find yourself on a nasty section, brake as much as possible before your front wheels hit it, just before your front hits the nasty bits take your foot off the brake to take the cars weight off the front and let the front suspension do its thing, if the car is well set up it will never kick sideways, worst case it might float a little, in that scenario just let it float/drift through making the required steering input to keep it straight ( this is the hard bit that should be learned early on in driver education ) if the road is not to bad and the surface is getting better not worse then just accelerate out.
I admit I have hit washouts that I didn't see or didn't realize how deep they were and have had to brake very hard, release the brake half a second before we hit it and then accelerate hard out to take the weight off the front so I didn't smash shockers and other suspension components.
Its all about balance not just sitting on 60km/h on every dirt road
 

2luxes

Well-Known Member
#33
I admit I have hit washouts that I didn't see or didn't realize how deep they were and have had to brake very hard, release the brake half a second before we hit it and then accelerate hard out to take the weight off the front so I didn't smash shockers and other suspension components. Its all about balance not just sitting on 60km/h on every dirt road
And how many average drivers can do that? The answer would most likely be a single figure percentage. Your description of what to do reminds me of Bathurst in 1974 when Jack Brabham and Stirling Moss came out of retirement to drive a SLR 5000 Torana. On practice day Jack's brake pedal went to the floor at 150 miles per hour and stayed there as he approached the end of Con Rod Straight. During a TV interview the next morning he said he put the transmission back to first gear to spin the car and wash off speed. He then brought it out of the spin and went down the escape road.

Us mere mortals can't do things like that. That is why so many cars out there end up on their roof and kill people far too often. Their drivers were faced with an unsealed road that was wide flat smooth and straight so they thought sealed road speeds were ok. Vic Widman did not write that magazine article just for something to do. The accident rate on Outback roads, particularly the ones that look like unsealed freeways, had reached the point where he thought it was necessary.

People with your experience are in an excellent position to explain the dangers and urge drivers to slow down, not cruise along at sealed road speeds.
 
#34
If I was living permanently in those areas I would be using heavy cross plies on split rims. For a one off trip, HTs with a bit of common sense thrown in are fine.

I called in to the Burke and Wills dig tree site ten years ago. The park ranger had 7.00 x 16 crossplies on his pre 2005 IFS Hilux and 7.50 cross plies on his family Nissan Patrol.

As for reducing pressures, I have only done that once in thousands of ks of dirt roads and mountain tracks and that was to drive to the top of Big Red and back down again.

I have also lived for a period of eleven years in rural NSW and I will be back there again as soon as we can sell our house. The local people don't get out and change pressures whenever they go from bitumen to dirt.

Having said that, some manufacturers tell you to reduce pressures. Cooper is one of them. I have only used Goodyear and Bridgestone on my current car. Goodyear's head office on their customer information service told me not to reduce them. The Bridgestones are the same specifications and also work perfectly on and off road on Toyota's recommeded pressures. The handbook pressures are so low anyway that I doubt if nobody would want to reduce them but they work both on and off road and dont wear the outside edges as they would if the pressures were too low.

So far my dirt road/track 4wd puncture record stands at one. That was two years ago on the Donahue Hwy near the NT border. I have had five in 2wd cars on sealed roads. The first was in the middle of the Sydney Harbor Bridge.
Agree with you regards to living out bush and deflating/Not deflating.
Normal road psi for me is 40, if I was to do the odt on 40, with a loaded 4B the ride would be far more harsh than at 28psi which is my normal to to psi when on outback roads. It's easier on your vehicle and the passengers imo. Only my opinion tho and what seems to work well for me, which might not work well for others, which I understand.
 

mikehzz

Well-Known Member
#37
Don't tell me you forgot to reduce the pressures. I have heard that makes them puncture proof on that road.
I was on 26psi and under 80kph. I think the tyre had history that I was unaware of. A rock broke through the tread. The guy put a patch inside at Oodnadatta but the same thing happened to the same tyre near Marree. All the other tyres were fine except the one that caught a nail in Marree.
Spooky, 9 years ago, the last time I was in Oodnadatta, I pulled up to get fuel and saw my drivers side rear rapidly going down. Exactly the same thing occurred yesterday, pull in to the Pink Roadhouse for fuel and drivers side rear rapidly going down. I'm not going there again... :)
 

peterfermtech

Well-Known Member
#38
Just putting a little science to it. Physics says that if you double your speed you increase your kinetic energy by 4 times. If you double the deformation distance then you halve the impact force. Make of it what you will.
regards
 

cam04

Well-Known Member
#39
Just putting a little science to it. Physics says that if you double your speed you increase your kinetic energy by 4 times. If you double the deformation distance then you halve the impact force. Make of it what you will.
regards
For the same reason it is harder to hole a 1/2 filled balloon, and conversely how highway pressure tyres chip out amazingly fast on graded rock roads. The worst parts of the plenty are sealed outside of Boulia now but if the grader had been through you wouldn’t make the border at highway pressure. Same on some Gascoyne roads in WA I’ve driven. I even chipped out a set at Mt Mee state forest during a lazy day trip. If you are anybody BUT 2luxes who has a unique situation with an old car and tyre that hasn’t been OE on any vehicle in 10+ years I’d highly recommend checking out the amazing amount of collective knowledge on Adam Plate’s (R.I.P.) hand drawn tyre guide shown above. You will never go wrong following it. Being lazy with tyre pressures is plain ignorant.
 

peterfermtech

Well-Known Member
#40
Just putting a little science to it. Physics says that if you double your speed you increase your kinetic energy by 4 times. If you double the deformation distance then you halve the impact force. Make of it what you will.
regards
Contrary to this of course is tyre flex with potential damage from the resultant heat build up and of course travel times. Like all things you need to pick your own point of compromise.
As I have no real experience on these roads, although in the process of planning a trip out there, I reckon I will go with cam04 and the "collective knowledge on Adam Plate’s (R.I.P.) hand drawn tyre guide shown above".
regards
 
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