Tread carefully with your tyres

Team D‑MAX has been riding its tyres mighty hard for the past 45 years

By: Dave Harding

Like a soldier in the jungle or a hiker on Everest, your ride is only as good as its boots. Take note when you choose your tyres...

Tyres are often the first and most significant modification that 4WD owners will make to their vehicle. Your tyres underpin the experiences you have in a 4WD, so first ask yourself: "Where do I want to go?"

There are three primary tyre tread patterns fitted to Australian 4WDs: Highway Terrain (H/T), All Terrain (A/T) and Mud Terrain (M/T). Each offers a different driving solution and experience.

Consider your lifestyle. Where do you go? What do you do there? How much time do you spend on sealed bitumen? And how much tackling off-road terrain?

Though the industry standard (see below) may not suit everyone, Toyo Tires technical manager (and 4WD tyre wizard) Steve Burke has seen many owners stray into A/T or M/T territory, only to spend their afternoon wandering the bush, searching for reception to call for a tow.

"It comes down to what you're going to do," he says. "Ten per cent off-road, for example, doesn't mean you can point your car into any terrain you like.

"Aussie terrain is renowned for sharp and hidden surprises and radical changes. A highway tyre can get you through plenty of off-road situations but you need to be mindful of tyre pressure and the capabilities of the tyres on your car."

Smaller gaps in the tread equal greater road-holding, larger are better off-road

The difference between tyre types relates to tread pattern and construction.

H/T tyres come standard on most 4WDs, including the Isuzu D‑MAX and MU‑X. With small gaps between tread blocks, H/Ts boast greater on-road grip, because they offer more contact with the bitumen, and reduced block flexing.

Their lighter construction makes them better suited to high speeds. Smaller block gaps reduce heat build-up and prevent blocks from squirming under load. Made primarily for tarmac, H/Ts are less suited to extreme terrain than A/Ts and M/Ts.

"H/Ts are street performers," says Burke. "Toyo's Open Country H/Ts are extremely low noise and offer ride comfort matched with fuel efficiency and a long tread life. I wouldn't take them to Cape York, but for the commuter who might use their vehicle on sand and for mild off-roading, they're perfect."

A/Ts are the middle ground between on-road and off-road performance. They're ideal for the driver who commutes, and then hits the beach or the bush on weekends. These are your all-rounders. Larger voids between tread blocks eject debris and provide good on- and off-road performance, without the noise or long distance comfort issues of M/Ts.

"A/Ts are often seen as a compromise with limited performance in certain terrains or poor traction in some street conditions, but that conventional wisdom is a bit limited," says Burke.

"A commitment to A/T tyre innovation, like that in the Toyo Open Country A/T II(OPAT II), has reduced road noise to levels similar to highway tyres, providing classleading mileage and proven class-leading mid-corner grip and wet and dry braking performance on bitumen.

"Normally, on-road manners in an A/T come at the expense of off-road performance, but the chunky OPAT II grips up through the toughest ruts or soft sand and is as hard as nails. Exceptional sidewall strength makes them ideal for motorsports, where unexpected punctures cost races, like the Australasian Safari or Finke Desert Race, where the Toyo OPAT II was a great success."

Some tyre manufacturers also offer a ‘severe service' A/T tyre.

"For us, this is the M55," says Burke. "It's designed specifically for rocky conditions where high loads are common, such as the mining/exploration market."

The trade-off is higher rolling resistance. Severe service A/T tyres usually have a higher off-road percentage compared with the industry standard for an A/T, typically 50/50 road/off-road.

At the rugged end of the spectrum are the M/Ts. Burly, purposeful looks give away their intention, with the wide, deep tread designed for situations where other tyres run out of grip. Tackling snow, sand, rocks, gravel and, of course, mud, M/Ts are built for the path less travelled. While they can have poor rolling resistance, be noisy on the road and require regular rotations to minimise irregular wear, their off-road performance is unparalleled.

M/Ts are the choice of the 4WD enthusiast or off-road racer, as well as the 4WD owner who wants a tougher look.

"As with the A/T II, modern technology has really made the M/T a much more street-friendly option than traditionally thought. We have a lot of reports of our Open Country M/T on daily drivers that see plenty of road use, keeping in mind that an A/T tyre will nearly always provide superior grip and lower noise on tarmac," says Burke.

"Most people who drive on M/Ts daily know the headache of ‘highway hum', especially on tour, but the OPMT is a much friendlier option. After all, there is bitumen between every adventure."

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