Heading off-road? One of the most important upgrades you can make to your 4×4 is to equip it with decent tyres. Here’s what you need to know when it comes to buying the right tyres for your 4×4.

CHOOSING THE RIGHT tyres for any vehicle is of utmost importance, but even more so with a 4×4, which can be driven in a variety of on- and off-road conditions, can be taken to remote areas, and can subjected to duties ranging from the daily commute to hauling a caravan on the big lap.

Depending on tyre size, a set of four quality tyres suited to the harsh conditions you’re likely to encounter driving in Australia will cost well over a thousand dollars, and if you’re heading into remote areas you’re also going to want one or two matching spares, considerably adding to your financial outlay. But when it comes to equipping your vehicle with the right rubber you don’t want to be a penny pincher.

Passenger Car Tyres

The standard tyres fitted to your shiny new four-wheel drive might look like they’re suited to off-road conditions, but in many cases they’re no tougher than the tyres fitted to your neighbour’s Corolla. This is because a lot of new 4x4s are equipped with Passenger Car (P) construction tyres.

If your vehicle is fitted with Passenger Car tyres, the sidewalls will either be marked with a ‘P’ or have no marking at all to indicate otherwise, and while they will be well suited to on-road driving, their light construction will not be compatible with the rigours of off-road driving.

Passenger Car tyres are lightly made for a variety of reasons. Light tyres are able to easily dissipate heat, which aids longevity, and they have flexible sidewalls that result in good on-road ride comfort. Rotational forces are also minimised with light tyres, which aids acceleration, braking and fuel economy.

While this light construction is beneficial on the road, Passenger Car tyres can be vulnerable to damage off-road; they don’t have good puncture resistance across the tread area and their flexible sidewalls can be prone to damage from sharp objects such as rocks, sticks and tree roots.

Light Truck Tyres

Four-wheel drive owners who do a significant amount of off-road driving, as well as those who just travel on crook secondary and/or gravel roads, should upgrade to a set of Light Truck (LT) tyres.

An LT tyre is built more heavily than a Passenger Car tyre, with extra strengthening in its sidewall and across the tread area. Tyre manufacturers do this by adding more plies (or layers) as the tyre is built, making those plies out of tougher materials, and by altering the design of the tyre carcass and the way it is constructed.

The tougher construction of an LT tyre enables it to better withstand the rigours of off-road driving thanks to much better puncture resistance in both the tread area and the sidewall.

Of course, there can be downsides to fitting LT tyres, such as a potential for increased fuel consumption due to higher rotational forces and a less compliant on-road ride due to the tyres’ stiffer sidewalls. But this is a small price to pay if it means the tyres won’t self-destruct off-road.

Light Truck tyres are clearly marked with ‘LT’. For example, on a tyre marked LT235/85R16: ‘LT’ refers to Light Truck construction; ‘235’ refers to tread width in millimetres; ‘85’ refers to aspect ratio (the depth of the sidewall as a percentage of tread width); ‘R’ refers to radial construction; and ‘16’ refers to the wheel diameter (in inches) that the tyre has been built to fit.

Tread Patterns

Tread patterns can be split into three categories – highway terrain (H/T), all terrain (A/T) and mud terrain (M/T), although there are many tyres that blur the lines between these categories, as well as others that are designed for competition use.

Choosing the best tread pattern to suit your 4×4 will depend on where you want to drive it. If you intend to do any off-road driving at all, you’ll want a tyre with a more aggressive tread pattern than a highway tyre.

Highway-terrain tyres are designed to offer good grip on the road, in both dry and wet conditions. They are also designed for long tyre life, minimal road noise and optimum fuel economy. While these are obviously desirable traits, H/T tyres don’t always perform so well off the road, their road-oriented tread patterns quickly filling with mud and unable to gain purchase in slippery conditions.

An aggressive tread pattern is one with wide-open tread blocks that will allow the tyre to get good grip in slippery terrain, such as in mud or on steep rocky hills. Most tyre manufacturers offer LT tyres in a couple of different tread patterns, and they will recommend one over the other depending on the amount of off-road driving you intend to do.

An intermediate A/T tyre has a tread pattern about halfway between an H/T tyre and a heavily block-treaded M/T tyre. An all-terrain tread pattern will suit four-wheel drivers who spend most of their time on the road but still need a more aggressive tread pattern for occasional off-road driving, or driving on unsealed roads or formed tracks. There are several A/T tyres on the market that offer comparable on-road performance and longevity to H/T tyres, combined with significantly improved off-road performance.

Tyres with a super-aggressive M/T tread pattern are designed specifically for regular off-road use in very slippery conditions where their open tread blocks can gain purchase and quickly clear themselves of mud. If you buy a set muddies just because they look tough, you’ll probably regret it; on the road they are noisy and offer limited wet-weather grip, and they will wear at a much faster rate than H/T or A/T tyres.

Load and speed ratings

Other information you can find on a sidewall includes a tyre’s load and speed rating:

Speed rating

J           100km/h

K          110km/h

L          120km/h

M         130km/h

N         140km/h

P          150km/h

Q         160km/h

R          170km/h

S          180km/h

T          190km/h

U         200km/h

H          210km/h

V          240km/h

W        270km/h

Y          300km/h

VR       >210km/h

ZR        >240km/h

Load index (maximum weight per tyre)

1 825kg

2 850kg

3 875kg

4 900kg

5 925kg

6 950kg

7 975kg

8 1000kg

9 1030kg

10 1060kg

11 1090kg

12 1120kg

13 1150kg

14 1180kg

15 1215kg

16 1250kg

17 1285kg

18 1320kg

19 1360kg

20 1400kg

21 1450kg

22 1500kg

23 1550kg

24 1600kg

25 1650kg

26 1700kg

It’s important to note that you must never fit a tyre to your vehicle with a lower load rating than that listed on your vehicle’s tyre placard.

It is allowable to fit a tyre with a lower speed rating than that listed on the vehicle’s tyre placard, so long as the driver does not exceed that speed on the road. In Australia the lowest speed rating for tyres with off-road features is ‘N’ (140km/h)

To ascertain your vehicle’s load and speed ratings you’ll need to locate the tyre placard, which on most 4x4s can be in one of the front doorjambs or on the glovebox lid. The placard will also have information on tyres sizes to suit the vehicle as well as recommended air pressures for different loads.

Tyre sizes

Depending where you live in Australia, there are different rules and regulations pertaining to the fitment of bigger tyres. In some states you can now lift a vehicle by a total of 75mm (50mm through suspension and 25mm through tyre-size increase) but it’s vitally important to check with your state’s governing body to ensure you don’t break the law.

What brand?

There are many tyre distributors in Australia and tyre prices vary significantly depending on the brand, tyre type and size, so how do you choose the right rubber for your vehicle? When you’re out driving and you spot a modified 4×4, have a look to see what tyres it’s running; check out what rubber is fitted to most of the vehicles the next time you’re at a 4×4 show; and ask the 4×4 enthusiasts behind the counter at your local four-wheel drive specialist.