The Art of Tire Design

Other than tires for the aerospace industry, commercial truck tires have arguably the toughest job in the tire business. It’s why tire makers dedicate so much engineering time to ensure their products perform safely and productively.

From a productivity standpoint -- since tires are the second-highest operating cost after fuel -- it’s important to look at miles to removal, fuel economy, and a price point for tires that is competitive. It’s what can keep fleets making money.

So, what makes tires so high tech? On the surface, they’re black and round and look pretty much the same. Commercial truck tire manufacturers all primarily use natural rubber for heat resistance and durability. By comparison, the automotive tires you drive on generally consist of more synthetic rubber than natural rubber.  And, truck tires all use carbon black to some degree as a primary ingredient in the chemistry of the tire. But that’s where the similarities end.

How to Talk Tiers

Some commercial tire brands are well-known and have been around for generations – proving their performance on North American roads. Others are less-known with limited distribution. And, as with any product, you have varying degrees of quality and expectations. In the tire world, those differences are expressed in terms of up to four tiers of quality and pricing-- with Tier 1 representing the best quality. And for the most part, you get what you pay for.

In defining the tiers, the lower the tier typically the lower the performance -- fewer miles to removal, for example. A Tier 4 tire might show up sporadically in the U.S. market, but then disappear. And there are a lot of players.

There are more than 250 different brands of drive tires listed on the Environmental Protection Agency’s SmartWay website; the vast majority in the lowest tier (Tier 4). The buyers of these tires are looking for rubber to put on the road – not high mileage, retreadability, or other metrics. They’re low-priced tires with casings that typically don’t hold up to multiple retreads. When you move up to Tier 2 and Tier 1 tires, you find a huge quality improvement, and casings with a 4-belt package. These tires give you long miles to removal, better fuel economy, and are engineered for multiple retreads.

One way to sum up the quality variant is to look at the tire manufacturer’s warranty. The better it is, the higher the quality. A tire manufacturer knows better than anyone else how its tires will perform. At Cooper, for example, we track performance data -- it’s why we’re able to offer an industry-leading warranty program.

When looking at a passenger tire versus a commercial truck tire, each has its own performance challenges for engineers. With a passenger tire, consumers are looking for handling, low road noise, and mileage in the 30,000 to 80,000 mile range. With commercial truck tires, it’s those attributes, fuel economy (SmartWay), plus casing integrity. Some fleets, with diligent tire maintenance practices, get more than 400,000 miles on drive tires.

Long-haul and regional operations each pose different challenges and that’s why wear, miles to removal, can vary greatly. The trick – or the art in what we do – is in balancing the performance attributes of the tire. The first five miles and the last five miles of a trip wear out a tire faster than the 500 miles in between.

Tire-eaters

Stopping, starting, and scrubbing tires (turning) are what wear away the tread and can impact uniform wear. So, as a tire designer, we have to figure out a way to resist those forces in order to make a better tire. Anyone can build a tire to go straight for 500 miles…and have good wear. But to get top performance you have to offset the forces that eat up a tire, or cause it to come out of service due to irregular wear. That’s the challenge.

Also challenging tire designers are the different wheel positions. Steer tires are considered the most important as they typically carry maximum loads and are very sensitive to tire pressure. And they’re constantly turning and scrubbing, and can be impacted by alignment issues. It’s why there is so much emphasis on engineering a tire that can withstand all the forces that come into play.

We’ve seen changes over the last 10- to 15 years as well.  In the past, the typical width of a steer tire was 8-1/2 inches – now it’s 9 inches. What this means is there’s a bigger footprint to spread the weight. And new compounds have made that tread roll easier over the road. Our new Cooper PRO Series LHS steer tire, for example, exceeds SmartWay rolling resistance standards by 15%. That’s a huge improvement. We continue to push the envelope to improve performance for our customers

Commercial tires are evolving at a rapid pace. Compounds continue to change and the mixes keep improving. The use of new raw materials and formulations allow us as tire designers to expand performance so that improvements can be made in rolling resistance while maintaining, or improving, treadwear and traction.

Another component in continued tire quality improvement is in the manufacturing process. To be considered a top tire manufacturer, tires coming off the line need to be uniform. And that means the specs and tolerances are very tight. For top tire brands, if the tires don’t meet spec, they’re rejected. And top brands, like Cooper, use x-ray and uniformity machines to inspect every tire coming off the line. Manufacturing commercial tires has come a long way. These improvements mean tires from the leading brands have better uniformity, which translates to longer, more even wear.

All told, it’s an exciting time to be a tire designer. We have so much technology and research at our fingertips. We have chemists with PhDs who uncover new ways to perfect compounding, and we have new ways to design and test our tires to ensure top performance. There is so much opportunity in the commercial tire space – it’s exhilarating to come to work every day to see what we can accomplish.

Editor’s Note: Phil Mosier is manager of commercial tire development for Cooper Tires. He is responsible for the design and development of commercial truck tires for the North and South America regions. This article was authored under the guidance and editorial standards of HDT’s editors to provide useful information to our readers.