Birth of a tire

Truck News

TORONTO, Ont. – On the surface, a commercial tire looks like a simple piece of equipment: round and black with a tread to grip the road. But Jeremy Miracle says otherwise.

“A tire is a highly engineered product,” says Miracle, a Goodyear materials engineer. “It has 20 or more components, and each might contain eight to 15 ingredients. Our job is to come up with the ratio of ingredients that deliver the performance characteristics that customers require.”

At the core of their efforts is a process known as “compounding.” In a nutshell, compounding is creating the recipe of ingredients for the different compounds that go into the various components that comprise today’s tires.

“I liken what we do to being a chef or a baker,” Miracle says. “It’s 99% science and a bit of magic.”

The process often begins with customers, who tell their dealer about something new they’d like to see in a tire.

Or it might start with comments from a field representative who has heard about a tire need in a particular application. The needs could run the gamut from improved treadwear, to increased fuel efficiency, to greater resistance to cutting, to more traction.

Engineers take that input and match it with what a specific compound should have to deliver the desired performance. Information then is translated into physical properties for the tire.

The engineers work closely with tire designers to create a product that will offer those properties. “It’s an integrated approach between engineering and design,” Miracle says.

Goodyear’s compounding specialists employ “predictive tools” that will simulate how specific compounds will behave. That information is passed on to finite-element-analysis modelers who work to predict how tires will perform.

Meanwhile in the lab, additional compounds are mixed to test properties. Then those results are given to the FEA modelers for more fine-tuning.

FEA modeling is a series of virtual tire drawings broken down into hundreds of small elements. The computerized drawings predict how the tire footprint will look under load, how it will respond when cornering, the amount of heat generation and what kind of strain the tire is likely to undergo.

“This is a computerized way to look at different development designs before you build the tire,” Miracle says.

Compound recipes begin with polymers, or what Miracle calls the “backbone” of compounds. Each polymer possesses distinctive characteristics and tire properties. For example, one polymer might be ideal for boosting traction, while another might yield longer tread life. Goodyear engineers utilize dozens of polymers, many of them produced in the company’s chemical division laboratory.

“Natural rubber polymers provide greater tear resistance and lower heat generation, while synthetics typically run hotter, which cuts into fuel economy,” says Warren Bush, head of commercial tire compounding at Goodyear. “Some tread compounds could be 100% natural rubber and some could be 100% synthetic. Synthetics are good for their flex properties, which translates into greater longevity of the sidewall.”

Synthetics are used less in truck tires than in passenger car tires, according to Bush. Goodyear materials engineers seek a balance between natural rubber and synthetics, depending on the tire’s application and desired properties.

“If we find a high amount of abrasion in stop-and-start applications, we may want to use synthetics more,” Bush says. “But if we use synthetics more, we might compromise its tear resistance.”

To the mix, engineers add reinforcing fillers for abrasion resistance, strength and durability. Softeners or plasticizers bond the materials together and aid in the manufacturing process, and protective chemicals are introduced to keep the materials from degrading and to protect the tire from ozone and oxidation damage.

During the curing process, the tire is subjected to high temperatures and high pressure. In this step, sulfur, zinc and softeners are added.

The tire development process typically runs from nine months to a year and a half, depending on the complexity of the redesign.

Compounding mixes known materials and materials yet to be developed to achieve prototype compounds that will go into a new tire.

For example, Goodyear’s self-sealing DuraSeal Technology uses a combination of on-the-shelf compounds and materials that had to be developed and fine-tuned for the manufacturing process.

“It was a long process that required adapting technology from the passenger vehicle market to commercial truck technology,” Bush says. “It was a formula modification that required time and innovation. It was a good example of successful compounding.”

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