Surface finish of roads affects tire wear
There are several factors that determine how fast the tires wear on our vehicles.
Many of them can be controlled by the driver such as using a smooth driving style, lowering vehicle speeds, keeping tire pressures correct and getting wheel alignments done as part of your vehicle’s routine maintenance.
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, sealed, 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 still good asphalt however, creates the equivalent of driving up a 1.75 per cent grade while 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 two inches (five cm) of snow is equivalent to climbing a 2.5 per cent grade, while four inches (10 cm) of snow is equal to a 3.75 per cent grade. Keeping those roads ploughed improves fuel economy tremendously.
A research paper commissioned by the Portland Cement Association also shows that concrete highways offer less rolling resistance than asphalt highways and the heavier the vehicle, the more difference there is. This is because asphalt is flexible and the heavy vehicles compress the surface more as they roll over it:
“Data indicates that fuel consumption of automobiles is not affected by the type of pavement surface. Pavement type greatly affects the fuel consumption of trucks,” says the Portland Cement Association study.
The same study indicates “25 per cent better mileage for a three-axle truck and 11 per cent better mileage for a two-axle truck (pick-up trucks and vans) on PCC (Portland Cement Concrete) pavement.”
Rolling resistance and fuel economy tells 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 sea shells in the region. It’s cheap filler. That type of surface tends to be pretty 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 U.S. they are using some ground rubber particles from used tires in the asphalt mix, forming a mixture they call ARACFC (Asphalt Rubber-asphaltic concrete friction course).
Note: the word concrete in this context refers to mineral particles bonded together with a binder agent, such as oils or resins.
According to a 2006 study done for the Arizona Department of Transportation: “Emission rates of tire wear per kilometre driven at PCC (Portland Cement Concrete) road surface are 1.4-2 times higher than emission rates of tire wear at AR-ACFC road surface.”
Concrete roads are expensive but last much longer that asphalt roads, stand up to heavy trucks much better and 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 and 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.