Safety Initiatives

Before the Rubber Meets the Road: A Visit to GM's Tire-Wheel Systems Lab

It's just 20 square inches on the road.

But the 20 square inches where a vehicle contacts the road are a critical element in determining how cars and trucks perform, handle and ride. Tire safety may be a recent topic of news coverage and public discussion, but it has been an area of focused research by General Motors Corp. since 1968. That's when the world's largest automaker assembled a team at its Proving Ground in Milford, Michigan, 30 miles west of Detroit, to help ensure GM's customers ride on outstanding tires.

"The reason this organization was formed was safety,'' said Jim Gutting, Director of Tire-Wheel Systems at the GM Proving Ground. "Everyone here at GM understands the sensitivity of tires. They are the critical interface of our vehicles to the road."

Jim Gutting's Tire-Wheel Systems team has spent over 30 years testing tires, making them ride more smoothly, handle better, and enable better vehicle fuel mileage. Gutting heads up a team of 60 engineers and technicians who helped develop the specifications and Tire Performance Criteria (TPC) for each GM vehicle. Major tire manufacturers Goodyear, Michelin, Continental-General and Bridgestone-Firestone, Pirelli, Hankook, and Maxxis produce tires for GM vehicles under the automaker's supervision.

"We work with the suppliers and we develop a statement of requirements that creates a set of specifications that align to our customer's wants and needs," Gutting said. "That leads to a very specific tire being manufactured for our product line. Our tires are designed specifically to meet our requirements from physical dimension perspective and vehicle performance perspectives."

GM's TPC (Tire Performance Criteria), like the tires themselves, are unique to General Motors. "We've benchmarked our processes against organizations around the world,'' said David Cowger, Engineering Group Manager for Tire Development, who has spent 22 years building a comprehensive body of knowledge with GM. "Our centralized engineering team has delved into tire issues for more than 30 years," Cowger said.

General Motors' bumper-to-bumper New Vehicle Limited Warranty includes original equipment tires. This means that GM consumers may bring their tire concerns directly to our dealers, which minimizes consumer inconvenience. Additionally, GM obtains valuable warranty and wear data.

"We work with tire suppliers and have a common database,'' Gutting said. "The data allows us to look at and understand the trends and lessons learned."

In General Motors' labs, tires in development are subjected to a series of rigorous tests under a variety of load and driving conditions. These tests measure critical performance characteristics including:

• Uniformity with vibration to ensure a smooth ride;
• Rolling resistance, which influences fuel economy;
• Moment of inertia, which influences brake system design;
• Force and moment properties, which influence steering;
• Load versus deflection, which influences clearance and optimum inflation pressures. (Click for more on GM's tire tests.)

From there, the tires move to the Proving Ground, where all tires are tested and retested for their acceleration and braking capabilities, stability and traction, and responsiveness in turns and evasive maneuvers. In all, hundreds of driving situations are replicated during the tests.

One of the most rigorous tests is the Accelerated Tire Endurance test, conducted under desert-heat conditions, such as those at the Bridgestone facility in Acuna, Mexico. Using special test vehicles that permit extreme loads, this grueling test measures the endurance of a tire (with a reasonable expected life) by introducing a range of loads, inflation pressures and road temperatures on highway, track and gravel surfaces.

To maintain the quality verified by all these GM tire tests, customers still should do their part to make sure the tires on their GM cars and trucks perform at designed specifications, Gutting believes.

"First and foremost is the responsibility to maintain tire pressure,'' he said. "There are other instructions in the vehicle's owner's manual about proper repair and maintenance of tires. The manual includes information on the importance of maintaining wheel alignment and how to properly rotate tires. There are also warnings about not overloading the vehicle. These specifications were designed to make sure your GM tires perform as designed."

According to Gutting, another important item for GM customers to consider is what tires they purchase as replacements. GM recommends that replacement tires have the same TPC (Tire Performance Criteria) number as the original tires. This means that the tires are specifically matched for the vehicle to provide consistent ride and handling for the life of the vehicle.

This thorough approach leaves GM confident in the safety of its vehicles, including the tires put on them. The company takes pride in the extra efforts devoted to the development of every system of the vehicle -- especially those that provide safety and security.

 

 

 

Content Owner: Richard J. Gratz, Engineering Group Manager, GM Tire-Wheel Systems.