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

Page 1 | Page 2 | Page 3 | Page 4

Heel and toe (cont'd)

When the tread meets the road, the downwards pressure increases. However, there is minimal abrasion here as the tread block begins conforming to the flat blacktop. After the tread has passed through the point of maximum compression against the road, it begins to leave the contact patch with the toe doing so first.

The toe leaves the surface with minimal fuss, like on its arrival, but it is at this point where the heel is still squashed against the road that most wear occurs. As the heel leaves the contact patch, it tries to return to its normal radius and the result is a scuffing action with the road. This scuffing action of the rear half of the tread block causes excess wear as the abrasion level is very high.

When a tyre is underinflated, or the load is too great for the given pressure, the angle at which the tread departs the road is reduced due to the longer footprint (remember slip zones). This reduced angle means a much longer scuffing action as the heel takes longer to depart fully from contact. As such, heel and toe tyre wear is greatly increased.

Heel and toe is also exaggerated on tyres with very blocky tread such as mud terrains. The reason is that the tread blocks are usually much longer and therefore suffer from a lot more movement under compression. Heel and toe wear reduces as the tread wears out, the tread blocks are shallower and the scuffing level decreases as a result.

The quick and easy answer to heel and toe wear is tyre rotation. Rotating the tyre (on non-directional tyres) effectively turns the heel into the toe and evens out the wear pattern. If not done regularly, or left too late, this wear cannot be evened out.

TREAT ME RIGHT

Simple maintenance and correct driving methods can eliminate abnormal tyre wear, so let’s take a look at what you can do to save your hard earned.

PRESSURE

One of the most important factors as far as a vehicle’s performance and economy go is the tyre pressure. A tyre is merely the carcass that makes up an air vessel. The air within it is what supports the weight of the vehicle, not the rubber. It doesn’t matter how good your tyres are, if they are not maintained to the optimum pressure then you’re not getting the most out of them.

Becoming complacent that your tyre pressures are right just because the tyre doesn’t look any different is not really ideal. Did you know that air can actually leech through the sidewall of a tyre, or can seep past the seal between rim and rubber? The air is always trying to find a way out of the tyre and as such is always deflating slowly.

However small this may be, it will start costing you dearly if not attended. Not only the costs through tyre wear, low pressure means a higher rolling resistance and therefore more loud pedal to achieve the same result when driving. As we all know, more loud pedal equals more fuel.

So what is the right pressure? After extensive testing in Australian conditions, the people at Bridgestone formulated a rule of thumb for optimum on-road tyre pressures.

Inside the driver’s door well there is a placard displaying the manufacturer’s recommended tyre pressure. Accounting for Australian road conditions and the continual variance in the load your vehicle carries, Bridgestone's recommendation is 10 percent above what the placard reads. If your pressures are under the placard’s figure then you’re underinflated.

For those of us who have changed tyre sizes from original, we need to find out what our vehicle weighs in a normal day-to-day environment (see your local weighbridge) and then contact a professional like Phil at Bridgestone. Thanks to the Tyre and Rim Association of Australia – Standards Manual, he can instantly use the weight of the vehicle and the new tyre size to give you the recommended tyre pressure for the load/tyre ratio.

Recommended tyre pressures are calculated on a cold tyre (25°C ambient temperature and out of direct sun), so the best bet is to check pressures in the morning before driving. A quality digital or analogue gauge is the way to go. Don’t rely on the in-built pressure gauges on the tyre inflators at your local servo – they’re about as accurate as measuring wind speed with a wet thumb.