Tires with excellent snow traction have received this special three-peak mountain snowflake symbol branded on the sidewall.

Are you ready for winter driving?

By Carin A. Helfer
As we watch the leaves fall, we know that winter is approaching. In Ohio, drivers know that winter will lead to snow and ice on the roads, but on that first snowy day, even the most experienced drivers need to remember winter driving habits. Interestingly, most drivers do not think about the most critical component of safe driving, whether on dry, wet, or snowy roads, which is their tires. Many drivers are not even aware of what the tire industry refers to as the “tire contact patch,” which is the amount of tire in contact with the road as we drive.
For one tire, the tire contact patch is relatively small and the total amount of rubber in contact with the road for all four passenger tires is about the size of a standard sheet of paper (8.5 inches by 11 inches). This relatively small amount of rubber is holding your car on the road, and is critical for safely driving your children to their activities, driving yourself to the grocery store, and traveling to grandma’s house for Thanksgiving dinner.
Over the years of producing tires, manufacturers have achieved significant engineering improvements that have led to more safe, durable, and fuel-efficient tires. The main purpose of tires is to conform to the irregular road surface and keep the contact patch as large as possible, under any condition, which is why the tire is made of flexible rubber. However, rubber products perform differently at different temperatures. If you have left a garden hose outside in the winter, you have seen it become stiff and inflexible. Because of these changes in the rubber properties with temperature, tire companies have produced tires designated as summer, winter, and all-season. Have you wondered what these designations really mean? Summer tires are made with a specific rubber compound and provide the following features: excellent handling and grip on dry or wet roads during warmer weather, better fuel economy, and reduced road noise. Also, compared to winter tires, these tires have fewer grooves and sipes. But, when the temperature drops below 45 degrees F (7 degrees C), the rubber compound in these tires becomes stiff and the tires are unable to grip as well. When this occurs, traction to the road is lost.
Winter tires have been designed to handle cold and snowy conditions because the rubber compound remains more flexible in cold conditions, which improves the grip to the road surface. In addition, the tire tread has deeper grooves and is heavily siped, which provides better snow traction. Unfortunately, the different rubber compound makes winter tires not suitable for summer driving. The tread wears quickly in summer conditions, which shortens tire life. These tires also have poor fuel economy, causing more trips to the gas station.
All-season tires were introduced by tire companies to handle a range of temperatures, even near freezing (32 degrees F/0 degrees C), dry or wet conditions, and roads with light snow. Most recently, tires with excellent snow traction have received a special three-peak mountain snowflake (3PMSF) symbol branded on the sidewall. These tires provide better grip on snow and ice than the traditional Mud and Snow (M+S) all-season tires. To receive the 3PMSF symbol, the tires must pass specific performance tests. In Ohio, our winter climate can be harsh enough that investing in 3PMSF tires is wise.
Regardless of the tire selection, some important safety checks that are often neglected with tires include safe tread depth and air pressure. Checking the tread depth is easy using a penny or a quarter placed upside down into the tread groove. If you see the top of Lincoln’s head, the tread depth is less than 2/32 inch, which in Ohio is not legal and will not pass an inspection. Most tire experts now suggest using a quarter. If the top of Washington’s head is visible, which indicates that the tread depth is less than 4/32 inch, the tire is legal, but not providing safe braking distances and should be replaced. The correct tire inflation is extremely important for proper tire performance. Overinflated tires reduce the size of the tire contact patch, reducing the grip to the road. Although, having underinflated tires may appear to be helpful because of an increased tire contact patch, steering and braking can be negatively impacted.
Even with the best tires, when the roads are wet, snowy, and/or icy, reduce your risk of an accident by driving at lower speeds and allowing for additional stopping distance. Although four-wheel drive vehicles can provide increased traction, four-wheel drive provides no improvement on braking. Some preparation before snow and ice cover the roads will help to ensure safe arrival to all your destinations.

Dr. Carin A. Helfer is a Research Assistant Professor in the Department of Food, Agricultural and Biological Engineering of The Ohio State University. E-mail: helfer.12@osu.edu; This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, the Sustainability Institute and the College of Food, Agricultural and Environmental Sciences.

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