Your tires know that not all road surfaces are created equal

by Jim Kerr . Jan 12 2018

There are several factors that determine how fast the tires wear on our vehicles.

A smooth driving style, lowering vehicle speeds, keeping tire pressures correct and getting wheel alignments done as part of your vehicle’s routine maintenance can all aid in extending tire wear.

Other factors such as weather and road conditions also play an important part in the rate of tire wear, but few of us consider what the actual surface of the road does to our tires every time we drive.

There are many types of roads, going from dirt lanes, gravel, asphalt and concrete. Not only does the type of road surface affect tire wear, it also affects fuel economy. For example, according to research figures from Ford, concrete road surfaces offer the least rolling resistance — although Canada does not have a large amount of concrete roads, favouring asphalt surfaces to endure our winter conditions. Smooth asphalt, when compared to concrete, is the equivalent of climbing a 1.25 per cent grade.

Rough but good asphalt, however, creates the equivalent of driving up a 1.75 per cent grade. Poor asphalt is equal to climbing a 2.25 per cent grade. It is not only cold temperatures that decrease winter fuel economy. Driving on five centimetres of snow is equivalent to climbing a 2.5 per cent grade, while 10 cm of snow is equal to a 3.75 per cent grade. Keeping roads plowed improves fuel economy tremendously.

Rolling resistance and fuel economy tell only part of the story. The surface finish of the road plays an important part. Think of the road as sandpaper. As your tire tries to maintain grip on the road, small particles are being worn off all the time. Some roads wear tires faster than others. Florida highways tend to contain a high shale content because of the abundance of seashells in the region. It’s cheap filler. That type of surface tends to be quite abrasive. Chip-seal road surfaces are used on top of both worn concrete and asphalt roads to extend their lifespan, but the sharp edges of the stones are very aggressive on tires. In Arizona and other parts of the country, they are using ground rubber particles from used tires in the asphalt mix.

Concrete roads are expensive, but last much longer that asphalt roads, stand up to heavy trucks much better, require less maintenance, but take longer to repair when problems do occur. Asphalt is cheaper in the short term, and quieter when considering tire noise, but needs to be replaced more frequently.

We have all seen those ruts in asphalt roads made by heavy loads. Grooving and textured roads use more fuel and wear tires faster, but may be necessary to reduce the risk of skids on wet or icy roads. The lighter colour of concrete makes it easier to see the road ahead when it is dark. As you can see, choosing the right road surface is not easy, but concrete is better for fuel economy.

As for tire wear, it comes down more to the content of the mixtures used in concrete and asphalt, and the type of surface finish, rather than just saying one is better than the other.

james.kerr@sasktel.net