Rolling resistance explained | Understanding tire dynamics

Tires continue to develop through the aid of modern technology. So many factors are considered when determining how to offer drivers the safest and most efficient ride. A variety of rubber compounds, combined with various tread patterns, tire sizes, and tires with a specific performance design have really allowed tire manufacturers the opportunity to create new kinds of tires that appeal to automotive engineers, as well as drivers who desire the ability to customize how their vehicles feel and perform.

One key aspect of tire engineering that tire manufacturers have focused on for years is rolling resistance. Rolling resistance is also called rolling drag or rolling friction. It is the resistance that occurs between the rubber and the road. In other words, it is the force that your tires and vehicle must overcome in order for your vehicle to move. This is based on several variables, not limited to road construction, road materials, tire design, and rubber compounds used in tires.

The Variables of Rolling Resistance

The first thing to consider about tires and their rolling resistance is the design of the contact patch. While a tire is a circular object, when it is placed on a vehicle and inflated to the appropriate PSI, it loses its completely round shape. The part of the tire that is flattened and maintains contact with the ground is known as the contact patch. This is also referred to as a footprint.

The contact patch is where rolling resistance affects a tire. There are several factors that are considered when constructing tires, including vehicle weight, compound construction materials, the spring force of the tread, as well as the stiffness of the tread and sidewalls. The research and development that goes into the development of a lower rolling resistance tire is quite exhaustive and impressive.

Tires that are inflatable will actually possess a lower rolling resistance than tires that are solid, regardless of the fact that they deform to meet the road surface. Inflatable tires, which are known as pneumatic tires, allow for more responsiveness to the road, as well as more resilience when your tire hits bumps, potholes, and other changes in the road surface. The rubber of a pneumatic tire and the fact that the tire is inflated makes it able to bend and flex to bumps in the road. This is one way your tires decrease their rolling resistance.

Variables such as tire size also play a key factor in rolling resistance. For example, many cars designed for high performance, sports cars, or cars that possess mid-engine or rear-engine design, often come with tires that are wider in order to increase the size of the contact patch. The compound used in these tires is also softer in nature, allowing for incredible cornering capability.

Both a larger contact patch and softer rubber compounds can increase a tire's rolling resistance. However, these negative effects on rolling resistance can be combated in a variety of ways. The contact patch on many performance tires is made larger by widening it rather than lengthening it, which lowers rolling resistance. While the rubber compounds in these tires are softer for better traction, they use components that have lowered their rolling resistances over their predecessors.

Low Rolling Resistance Tires

Over the past decade, nearly every major tire manufacturer has begun to develop low rolling resistance tires. These tires have been fitted as original equipment on some of the world's most popular cars including the popular Toyota Prius with its 50+ miles per gallon. Nearly every automobile that has been designed to be economical and fuel-efficient now boasts low rolling resistance tires from one of the top tire brands.