Tyre Pressure Misinformation Alert – South Australians especially!

This is a quote from a training organisation:

“Adhering to the manufacturer’s recommended tyre pressures is not only essential for vehicle performance and safety but also a legal requirement under various Australian road traffic laws.”

They also say that there is no need to deflate tyres even for sand/beach driving, and have suggested that anything other than recommended pressures voids your insurance.

This is both incorrect and dangerous advice, and is based on a misinterpretation of words, a disregard of clear evidence, and faulty logic. I very rarely write these sorts of posts, but this one needs to be countered as it is a safety problem. This is why that view is wrong:

Let’s first look at the manufacturer’s wording. If the carmarker sets a clear limit, then they use wording such as ‘never’, ‘must’ and ‘always’.

For example from the Ranger manual:

“Always determine the depth before attempting a water crossing. Never drive through water that is higher than the bottom of the wheel hubs.”

That’s very clear, isn’t it? Which is kind of odd given that depth is 400mm and the wading depth of the Ranger is 800, but that’s the owner’s manual for you. It would be interesting to see if that organisation teaches Ranger drivers to exceed that depth during wading. Or if they follow Toyota’s advice to only engage lockers when you’re stuck.

Back to the manual, this time for towing – “Do not exceed the load limits.”

Again, very clear wording. Now for tyre pressures:

“At least once a month and before long trips, inspect each tire and check the tire pressure with a tire gauge. Inflate all tires to the recommended inflation pressure.”

Nowhere will you find a must or never or always for the tyre pressures. It’s always recommended, and it’s recommended not mandated because the manufacturer recognises tyre pressure needs vary but a baseline is needed.

And, if you look at manufacturer provided, endorsed or certified offroad training…then it will include tyre pressure reduction appropriate to the terrain. Again from the Ranger manual:

“WARNING: Always re-inflate tires to recommended tire pressures before the vehicle is operated on-road. The recommended pressure is located on the tire label or safety certification label, located on the B-pillar, inside the driver’s door.”

Yes, Ford assumes you’ve aired down for offroad. How’s that recommended pressure looking now?

This is what manufacturers say when they set exact limits:

“Retighten the wheel nuts to the specified torque within 160 km after any wheel disturbance, such as tire rotation, changing a flat tire or wheel removal.”

The torque for Ranger wheel nuts is 135Nm per the owner’s manual. Clearly, 135 shall be the number thou shalt count, and the number of the counting shall be 135. 136 shalt thou not count, nor 134 excepting that thou shalt proceed to 135. And if you don’t make it 135, you are naughty in the eyes of Ford, and may snuff it. There is no different torque for onroad, or offroad. Unlike tyre pressures.

And then:

“Installing wheels without following these steps can cause the wheel nuts to loosen and the wheel to come off while your vehicle is in motion, resulting in loss of vehicle control, personal injury or death.”

You won’t find such dire warnings about deviating a from a precise recommended tyre pressure. Manufacturers, being risk averse, are quite fond of the “personal injury or death” warning. Here’s another:

“Exceeding any vehicle weight rating can adversely affect the performance and handling of your vehicle, cause vehicle damage and can result in the loss of control of your vehicle, serious personal injury or death.”

So if there’s a real limit, you’re warned of death.

Then come to the law. Here’s an example:

“ADR 42/04 – General Safety Requirements: This rule stipulates that vehicles must be maintained in a safe and roadworthy condition.” – I’ve quoted the training organisation here, as they are correct.

A “safe and roadworthy condition” is a broad term, and nothing in it, or any other regulation, states that you must run any specific tyre pressure or that the pressure be a manufacturer’s recommendation. Why? Because the manufacturer has to give you a baseline pressure which is safe enough for the majority of users the majority of time.

What the road authorities wants, and your insurance company wants, and every other road user within your vicinity wants, is safe operation of a vehicle. This means choosing an appropriate speed, gear and of course tyre pressure consistent with the specific combination of vehicle, load, speed and terrain at hand.

It is safer to drop tyre pressures to say 15 for a beach drive under 30km/h than to struggle on with road pressures, getting bogged, working hard to free the vehicle, causing blockages for others, and creating ruts. And nothing in the law, manufacturer recommendations, or your insurance PDS says you can’t.

Now if you left the beach and drove home on bitumen at 15psi that would be irresponsible as you’d severely impair your car’s handling and quite possibly explode a tyre – refer Ford’s warning. Same way if you tried to drive home in low range or with the centre diff locked. You have to set your vehicle up for the task at hand, and that includes varying tyre pressures.

Some organisations take a very simplistic view of vehicle setup, including banning non-placard tyre pressures, changing wheels, carrying out recoveries and so on. This is because they have to manage their risk very carefully and cater to the lowest common denominator as they have an OldMate58 running a department full of Sheal Berites. That is their rule, and it doesn’t follow that it applies elsewhere. Some military people are quite fond of commenting on my videos telling me I’m wrong because That’s Not The Way We Did It In The Army.

Finally, it is legal to fit tyres which are not listed on the tyre placard. I have a whole video on this exact topic because what tyres you can legally fit is a complex question. Different tyres work best with different pressures (see the manufacturer recommendation placard for proof), and then there are also GVM upgrades to consider.

If you want to see the effect of tyre pressures in sand also watch my pressures video where I ascend a dune at 40psi working down to 10psi. If that alone is not evidence enough that low pressures work in sand then I don’t know what is, but then again OldMate58 is still battling away against lever principles, mechanical advantage and every other law of physics bar gravity, claiming the counter arguments are only flesh wounds.

You can also consider that tyre manufacturers have blog posts advising customers to drop pressures for sand. And most parks with sand driving have signs advising the same. Government agencies aren’t going to do that unless it’s legal and safe.

Please continue to vary tyre pressures for the driving conditions you encounter, and ignore anyone who suggests otherwise because correct vehicle setup is an important safety issue. You need to differentiate between recommendations and specific limits, then apply your understanding of principles to arrive at a safe setup, which is what training should be all about.