Manufacturers of both tires and vehicles spend a great deal of time figuring out the proper air pressure for optimum safety on vehicles. Using chalk across the tread of a tire to see if the entire tread touches the ground at parking lot speeds is not a scientific approach to determining proper tire inflation.

It’s an anecdotal measuring stick to try and improve tire wear by creating a larger tire contact patch. The theory is the wider contact patch will prevent the center of the tire from wearing faster.

The Problem with Chalking

The idea that the entire tread of the tire needs to touch the road is the first issue. Lowering the air pressure to reach this state doesn’t take into account tire flex, sidewall rigidity, or tire temperature. The last one is the fiasco that almost ruined Firestone tires and plagued early Ford Explorers with dangerous blowouts and rollovers.

We posed this question to some of the tire partners we work with and these are a couple responses.

From: Fardad Niknam, Yokohama Tire senior director of Consumer Product Planning and Product Marketing said: “We only recommend the air pressure as recommended by vehicle manufacturers. Chalking tires is a good practice to find out how the contact patch looks like and how much is on the road.”

From: Gregg Vandermark, Continental Tire the Americas, LLC said: “For street use, we recommend proper vehicle performance rating/load index and using the manufactures door jam inflation recommendation/table.  As when driving on public roads/streets there are other safety factors to consider beyond tire wear.”

Tire tread isn’t designed to be perfectly flat on all tires.

The Dangers of Underinflated Tires

“According to the National Highway Traffic Safety Administration, almost 1/3 of passenger cars, light trucks and SUVs are being driven with at least one under-inflated tire.

Under-inflation is one of the leading causes of tire failure. If tire pressure is too low, too much of the tire’s surface area touches the road, which increases friction. Increased friction can cause the tires to overheat, which can lead to premature wear, tread separation and blowouts.” (NHTSA)

Tires have a safe operating maximum temperature before the rubber begins to break down and the mix of silicates, rubber, steel, and fabrics begin to separate.

Underinflated tires are prone to sliding, excessive body roll, loss of control, and do not allow the tread to properly evacuate water. Interesting underinflating tires also promotes higher tire wear, the exact condition so many swear they are preventing.

The Wrap

I may not change anyone’s mind with this article, hopefully, it’s possible to prevent at least one person from running underinflated tires and possibly prevent an easily avoidable accident.




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William Connor

As the Editor, William is responsible for all the good, the bad, the ugly and the indifferent that happens at 4WAAM. William brings a wide range of experience to this role. He also wields a freely shared...

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    1. Monty,
      The vehicle’s weight dictates tire pressure, not tire size. That’s why large 1-ton pickup trucks run 60PSI in tires far smaller than our off-road tires.

      Tires are not designed to run flat edge to edge on the road surface.

      That’s why I also don’t recommend running a tire that has a load range above the vehicle’s weight category. The vehicle won’t be heavy enough to flex the tire and make good use of the available traction.

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