Test all limits in the Nissan Navara
Test all limits in the Nissan Navara

All is not equal in all-terrains

The term ‘‘all-terrain,’’ or AT, is commonly used by tyre manufacturers to describe their off-road products. Unfortunately, this well-known phrase tells only half the story – and is a bit misleading.

Sure, traction is vitally important for any off-road tyre; but when was the last time you saw a 4×4 spin hopelessly out of control because the tyres’ tread pattern wasn’t designed properly? I’m guessing… never? Why? Because most tyres offer a reasonable degree of traction on a variety of surfaces, with the exception of mud. This raises the question: What makes an off-road tyre a true off-road tyre? I believe the answer is simple: strength.

off-road tyre

Although the market is brimming with so-called all-terrains, in my view, very few of these brands are genuine off-road products in terms of carcass construction, rubber bulk, and material compound. In other words, their tread pattern may say ‘’off-road’’ but their carcass construction is not much different to that of a road-biased, or highway-terrain (HT), tyre. If you’re not convinced by this, perform a basic test yourself: pick up the tyre and feel its weight. The fact is, lightweight tyres are made with less rubber, and heavyweight tyres are made with more rubber, and the only reason why a tyre would be made heavy in the first place, is for strength. It’s certainly not for economics.

So, why do so many tyre manufacturers bother to make an AT tyre that fails to deliver core off-road benefits such as strength? It’s another simple answer: price. Lightweight tyres are cheaper to make, cheaper to sell, and more likely to pull big sales figures. Another big selling point is that lightweight tyres are quieter, more comfortable, and more fuel-efficient on-road. If those last three points happen to be exactly what you want from an AT tyre, and you don’t plan on travelling much off-road, congratulations, you’ve saved some money in the short term. However, if you’d like to know how to identify a true off-road product, keep reading…

The secret lies in a common tyre term known as ‘‘LT’’ or ‘‘light truck’’. An LT tyre is the off-road alternative to what’s known as an SUV tyre. We could get into the origin of the term, but what matters here is that ‘‘LT’’ loosely refers to the load-ability of a tyre, and therefore, its strength. To put that another way: if a tyre doesn’t say ‘‘LT’’ on its sidewall, there’s a good chance it’s a lightweight tyre and not a true off-road product.

off-road tyre

If you keep reading along the tyre’s sidewall you’ll also notice a load range letter. This alphabetical symbol (recognised by the global tyre market) equates tyre thickness to a comparable ply rating. For example, the letter ‘‘E’’ written on the side of a Cooper Discoverer S/T Maxx (265/65/R17) suggests that the comparable sidewall rating would be a 10 ply. Other rating symbols include a C (6 ply), or D (8 ply). However, the notion of equating rubber bulk to a ply count is a bit outdated, and refers to the old tube-type design.

What’s more, if you compare the weight of the abovementioned Cooper against a well-known OE specification all-terrain (using a 265/65/17 as an example), you’ll find that the Maxx weighs in at 24.5kg, while the OE tyre tops the scale at just 18.2 kg. (That’s 35% more rubber!).

So, if you’re in the market for a new set of tyres, and you specifically want durability to feature high on the list of qualities, you may want to ‘‘weigh up’’ all your options.

By Grant Spolander

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