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How to manage tyre pressures

By Sean Muir, 25 Dec 2015 Gear

How to manage tyre pressures

Tyre pressures – everyone has an opinion. But not everyone is worth listening to. 4x4 Australia talks to a veteran four-wheel drive trainer to get his top five 4x4 tyre-pressure tips.

When it comes to opinions on tyre pressures, there is a lot of hot air out there – especially online.

Thankfully, there are a few characters who don’t base their expertise entirely on the fruits of Google.

Adventure 4WD Director David Wilson is one of them. He has been a four-wheel drive trainer since before Google was a thing, and now works closely with the guys at Toyo Tires. Among other things, he’s also the face of Isuzu’s I-Venture Club. We had a chat with him recently to get his top five tips for managing tyre pressures – with any luck they’ll help keep you moving. This is what he reckons…

1. Start with your tyre placard for on-road pressures
Let’s start with your on-roads. Most of us drive around on bitumen roads most of the time, so paying attention to your tyre placard and what it says is your starting point. Most wagons and utes start at about 200kPa/29psi and go up to around 250kPa/36psi when laden.

These pressures will work on the blacktop for 99 per cent of drivers. But we see over-inflation all the time and it’s stupidly unnecessary, wearing tyres out prematurely, increasing puncture susceptibility, extending emergency braking distances and more.

Don’t do it.

2. Follow the ‘20 per cent’ rule
When you venture on to a dirt road, those bitumen pressures will be too high and can contribute to a loss of control. We’ve coined our ‘20 per cent rule’ (see the Toyo Tyres website www.toyotires.com.au for a full explanation) and it works a treat when travelling big distances on dirt roads.

In a nutshell, if you’re going to be on dirt for a while, let 20 per cent of the placarded pressure out and slow down by 20 per cent. So, with now early-mid 20s psi and a maximum speed of 80km/h, you’ll have a tyre that’s flexible and able to absorb the bumps, and defeat most puncture events, to give you a more comfortable ride and shorter emergency braking distances.

3. Keep going down
As the track-space further deteriorates, keep incrementally letting more air out until you reach a point where traction and momentum is restored and progress is once more a breeze. Remember, though, with each deflation your speed, too, needs to incrementally reduce so the tyre doesn’t get hot and bothered.

4. Don’t go too low
Your minimum pressure should be 100kPa/15psi for all but emergencies (or what I sometimes call divorce pressures – you know, bogged on a beach with a rising tide!). At 15psi or less you’ll need to be really, really careful about your steering, braking and accelerator inputs as there’s now so little air in the tyre it might come off the rim.

5. Pump them back up
At day’s end pump your tyres back up to an appropriate pressure for the surface you are driving on. The fastest way to do that is using an air compressor like ARB’s twin motor compressor – those things are fast! Check the pressure with a reliable dial-type gauge of metal construction.

David Wilson is the director and lead trainer at Adventure 4WD, based in Adelaide. Visit the Adventure 4WD website at www.adventure4wd.com.au for more information on training and services.