Do you know anything about low rolling resistance tires?

Jul 29, 2023

Low rolling resistance tires ：a simpler way to save fuel.

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In the "Low Rolling Resistance Tire Confidence Report" released in April 2020 by the American Council for Freight Efficiency, Yunsu Park, the Director of Engineering, pointed out that "rolling resistance accounts for 30% to 33% of the fuel costs of trucks. Low rolling resistance tires are a simple way for fleets to reduce fuel consumption, and most importantly, they hardly increase costs.

Looking at the world as a whole, the earliest case of long-haul heavy-duty trucks using low rolling resistance tires occurred in the United States in the 1990s. A transportation company called Schneider National replaced its fleet's tires with low rolling resistance tires in 1998, and according to test reports, its fuel efficiency improved by 3.5%.

Although a 3% improvement in fuel efficiency may seem small, it can translate into significant fuel savings and reduced operating costs for heavy-duty trucks that operate for long periods of time.

Why do low rolling resistance tires save fuel?

"What makes the use of low rolling resistance tires fuel efficient" and what is so amazing about them? As a matter of fact, they are fundamentally different from ordinary tires in terms of tread pattern, material application and tire structure, etc. These features make low-rolling resistance tires generate less heat and friction during driving, thus greatly reducing fuel consumption.

Relying on special tire tread patterns

Firstly, in terms of tire tread patterns, Tim Miller's research team from Goodyear Tire Company explained that for non-low rolling resistance or high traction (high grip) tires, the tread patterns are wider and deeper. When the tire rolls, the deformation and compression of the tread blocks are greater, which results in more energy consumption. However, for low rolling resistance tires, their characteristic is that the tread is thinner and more rigid, and the compound is harder. When the tire rolls along the road, the degree of deformation of the tread is smaller, resulting in less energy consumption.

That is to say, the tire that wastes the least amount of energy when rolling on the road is the more efficient tire. An extreme example of rolling efficiency is the steel train wheels on steel rails. Both the wheels and rails have smooth polished metal surfaces that deform very little. However, due to the low coefficient of friction between steel and steel, the traction is poor.

Currently, manufacturers are producing tires with closely spaced tread patterns. When the tire tread rolls, these tread patterns can be tightly squeezed together and support each other. This leads to less deformation of the tread and not only reduces rolling resistance but also minimizes the reduction in traction.

Relies on more wear-resistant materials

In the development history of low rolling resistance tires, as early as the early 1980s, low rolling resistance energy-saving tires with lower aspect ratio and shallower tread patterns appeared on the US market, which could improve fuel efficiency by 3%-4%. However, due to the limitations of material technology at the time, their price was 15% higher than that of ordinary tires, and the tread life was reduced by 30%.

At that time, diesel prices were low worldwide, so the fuel-saving advantage they had was difficult to offset the disadvantages of "higher cost" and "shorter life", and they were not recognized by the market at that time.

As time rolls on, with the outbreak of the oil crisis, the high fuel prices have rekindled the industry's attention to "energy-saving tires", and more companies have joined in the research and development of low rolling resistance tires. There are three main factors to consider in tire design: rolling resistance, traction, and service life, as well as three secondary factors: retreadability, ride quality, and cost.

When one of these three main factors is significantly improved, it will lead to a decrease in the other two factors. For example, "if the rolling resistance performance of the tire is greatly improved to pursue the ultimate low rolling resistance, its traction and service life will be significantly reduced.

According to the "Low Rolling Resistance Tire Confidence Report" of the United States in 2020, "the cost savings of longer tread life exceeds the fuel savings achieved by reducing rolling resistance by 10%." However, with the continuous progress of modern material technology, "reducing rolling resistance" and "higher tire life" are no longer a simple trade-off relationship.

When more synthetic materials are applied to low rolling resistance tires, it can minimize the impact on traction and tire life while reducing the rolling resistance coefficient as much as possible. This makes it no longer a problem to make low rolling resistance tires more durable.

Relying on a more rational tire structure

In addition to making changes to the surface of the tire, there is also potential to optimize the interior of the tire. According to Michelin, in terms of rolling resistance, the tread usually contributes about 40% to the tire's rolling resistance, the sidewall and the belt layer contribute another 40%, and the bead area contributes about 20%.

To reduce tire resistance, the simplest method is to start with the tire sidewall and increase its hardness. This is because the less the sidewall bends, the less energy is consumed. However, excessively increasing the sidewall hardness can also lead to a decrease in the tire's impact resistance, so a balance needs to be struck between hardness and impact resistance.

Rely on uniquely customized rubber

Each manufacturer produces tires of each model with its own unique material mixing formula. Engineers also design different rubber compounds for different applications. For low rolling resistance tires, it is most important to reduce the overall elasticity of the tire (including the tread, sidewall, bead, and interior of the tire), because this can shorten the process of returning to the original shape when the tire is deformed, thus consuming less energy.

Of course, low rolling resistance tires aren't everything.

Fuel efficiency and energy saving are good things, but we should be aware that in many operating scenarios and usage conditions, it is not recommended to use low rolling resistance tires. The main reasons and scenarios include:

Heavy and overloaded transportation: Low rolling resistance tires often reduce rolling resistance by sacrificing weight and thinner tread. In heavy and overloaded transportation scenarios, these tires may not be able to withstand excessive loads, which can easily lead to tire damage or blowouts.

Poor road conditions: In harsh road conditions such as sand, mud, or snow, the tread depth and pattern design of low rolling resistance tires are often not as good as specialized off-road tires, which may affect grip and handling stability and reduce driving safety.