Goodyear, the ACCC and Green Tyres
So Goodyear Tyre and Rubber have been pinged by the Australian Competition and Consumer Commission (ACCC) for making claims that their tyre was “green”, without being able to substantiate the claim. According to the ACCC, over the last two years, Goodyear Tyres made a number of representations regarding the environmental benefits of its new Eagle LS2000 range of tyres such as the production process led to reduced carbon dioxide emissions and the tyre would use less fuel on the road.
So what makes a “green” tyre? First, for the tyre experts amongst us, a “green” tyre is an assembled tyre that hasn’t been vulcanised yet. That’s not what Goodyear was about.
A “green tyre” can be summed up in three words- low rolling resistance. As a tyre revolves, it absorbs power, which is ultimately sourced from the fuel that you put in the tank. The lower the rolling resistance, the lower the heat generated inside the tyre, and the lower the fuel consumption. It absorbs power because it is distorting where it hits the road, and recovering its shape, during every revolution. All those little molecules are being made to spring back into shape (they’re elastic, but not perfectly so), and in so doing, they lose some energy as heat.
Fortunately, this resistance is easily measured on a dynamometer equipped with a torque reaction weighing head. Typically, a brand new tyre will absorb more power than when it is “run in”. Fit a flexible coupling to the hub so that the tyre can have its pressure adjusted on the fly, and the effects of raising the inflation pressure can be easily measured – less distortion, less energy consumed, less fuel required to drive it. Which is why motoring authorities and environmental advocates advise motorists to inflate their tyres to the higher of the pressures placarded on the vehicle.
How does the tyre engineer set about designing a tyre specifically optimising its low rolling resistance?
Easy!!!!! Just reduce the volume of rubber in the tyre, by making the tread depth less, and reducing the rubber volume in the shoulder/buttress area of the tyre- the thickest part. They do this by rounding the profile of the tread arc to lighten the rubber gauge in the shoulders. Unfortunately though, a rounder tread radius does not wear as well as a flatter radius, though there is a limit to how far you can go with this too.
So the end result is a lighter tyre, absorbing less power, that doesn’t go as far. But there is another factor- it’s called the Australian country road, with its broken road shoulders, and potholed edges. Lighten the tyre, and the durability under country conditions is less. How do I know? Been there. Done that.
During the oil shock of the seventies, when oil when to the equivalent in today’s dollars of (shock horror) $80 a barrel, the company for which I worked brought out a tyre based on these well-known design principles. Unfortunately, by the time it was developed, the oil shock was over. Stuck with a slow moving item, the fateful decision was made to release them in far away Australian markets where they would not disrupt the existing price structures- i.e. ‘ the outback”. The result- disaster!
What is interesting today is the number of tyres that now carry words in their branding that implies that they are eco-friendly, as part of the pattern code, or whatever. Since nearly all tyres are fully imported, and manufactured all over the world, the ACCC.may have a busy time checking out such claims.