Words and Photography by Bryan Grant
Header photo by Robb Cox
Diagrams courtesy of Bridgestone Australia

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They hold you up, they take you forward and they do the heel and toe! You can’t stop your tyres from wearing, but you can minimise it and save dollars to boot.

It’s common for people to take the concept of tyre maintenance for granted. After all, you walk out and the fourby looks the same as it did yesterday, so jump in and let’s go. While the cost of living continually rises to please the economy god, every cent we save will help elsewhere. You would be surprised how some simple routine checks can save you money by maximising the life of your tyres.

Who better to speak to about tyres than the experts? To gain an insight into the factors affecting tyre wear and to discover some of the science behind it, I spent an interesting day at Bridgestone with tyre guru Phil Burnard.

Wear me out

No matter what you drive, how you drive or where you drive, your tyres will always ‘wear out’ to some degree. As your vehicle rolls along, there are constant ‘shear forces’ that cause parts of the tyre’s tread to slip. This in turn creates an abrasion between the tread and the road surface. Friction between the tyre and road creates the grip that we utilise every day when accelerating, turning or stopping.

When you think about the tyre’s road contact in that way-it makes it easy to see why your tyres wear. Let’s take a look at wear types, and what influences them.

Slip zones and wear

Just like the process with a criminal’s thumb, if you dipped your 4WD’s tyre in ink and then dropped it onto some paper, the tread would paint a footprint showing the contact with the road.

Looking at the example footprint, you can see that the greatest pressure is applied in the centre of the print. A high level of pressure applied here means it has the greatest friction levels and road-surface grip.

As we move away from the centre, the pressure between road and tyre decreases. Places of lesser grip allow movement between the tyre and the road to cause scuffing and higher wear rates.

Areas of higher wear are mostly affected by under-inflation, or when a higher load is applied to the original tyre pressure. These influences considerably lengthen the tyre’s footprint, and the range of the high-slip zone also lengthens dramatically.

Heel and toe

No, I’m not talking about the primary school dance here. Thanks to the previously discussed slip zones, we come to the tyre’s unpreventable wear characteristics known as ‘heel and toe’, and it’s an interesting one too.

Heel and toe refers to the tyre’s individual tread blocks, with the toe being the leading edge, or that which contacts the road first as the tyre rotates, while the heel is the trailing edge that is last to leave the road’s surface.

You have probably seen examples of heel and toe wear before and wondered how it happens – I know I have.

Heel and toe wear is the pattern that forms when the trailing end of the tyre’s tread blocks wear out faster than the leading edge and causes a jagged or ‘saw blade’ type appearance. This is one tyre-wear property that seems to go against all logic. One would imagine that the leading edge of the tyre that contacts the road first would be the quickest end to wear. Wrong!