Technology Countdown: Tire safety

February 26, 2013, Pat DeCola, NASCAR.com

Tire safety

There's more than meets the eye when NASCAR tires hit the track.

A simple, often overlooked piece of equipment in the eyes of NASCAR fans, the tire’s importance to stock car auto racing cannot be emphasized enough -- especially considering it’s the only part of the vehicle that actually touches the racetrack.

The Goodyear, yellow-lettered EAGLE tire is currently the only one used in NASCAR, and has been since 1997. Goodyear hand makes every racing tire for all three NASCAR series, and it makes more than 100,000 tires for NASCAR in a season.

In 1966, Goodyear developed the tire-within-a-tire concept, named the Lifeguard Inner Liner Safety Spare, which is still used today. It creates a second envelope inside the main tire to prevent a full blowout, allowing the driver to return to pit road safely to change the flat. NASCAR rules require that all tires must have an inner liner on tracks that are over a mile long.

The current tire has a rubber-coated bundle of steel wires that runs along both inside edges of the tire and seals against the wheel, while an inside layer of rubber holds nitrogen gas. The next layer is the belt package, which provides strength and resists puncture to the outermost layer.

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Tire technology has since become such a precise aspect of NASCAR that crews have plenty of access to information about a specific tire or set. Goodyear prints a barcode on each tire that, when scanned, provides an entire history and list of specifications for that exact tire.

As an example of how this is helpful, at all races except the two road courses, the left side tires have a slightly smaller circumference than the right side (87.4 inches versus 88.6) to help the car corner. However, some tires can be off by a 10th of an inch after production, so crews will group sets of tires together by precise circumference, the date it was manufactured and even the shift it was produced, all thanks to the barcode.

While what we see in the wheel wells of a car such as 2012 Sprint Cup champion Brad Keselowski’s Ford Fusion may serve the same primary function as the ones on our own vehicles, there are, of course, some major differences aside from the inner layer.

First, NASCAR tires have a vastly different look to them. Where the idea is to enhance the grip by getting as much of the tire to contact the racetrack as possible, there are no tread marks on stock car tires. It gives the tire a completely smooth look. Since NASCAR races are only run on a dry surface and stopped during periods of wetness, treads are unnecessary.

The reason NASCAR tires are inflated with nitrogen, rather than the normal air we pump into our tires, is due to the increased stability under hotter temperatures that the gas exhibits. It allows the tire pressure (50 pounds per square inch) to remain constant throughout the race regardless of the temperature, which can reach 200 degrees Fahrenheit.

Different tracks require different tire compounds, as regulated by NASCAR officials. A softer tire provides a driver more grip but wears out faster depending on the track surface, tightness of turns, number of turns, and type of banking each track offers.

Another thing that NASCAR tires experience during a race is the slip angle, which happens when the car is making a turn and the tires point one direction and the wheel points slightly the other way. It can be utilized to the driver’s advantage to maximize turning force, but anything more than a two-to-four degree angle risks an amount of skidding that forces the car out of control.