Racing Tire Maintenance - A Little Respect

A tire appears to be the simplest item on a racecar. But to the contrary, the quality of racing tires is one of the most important factors determining how well a team performs. If team members are not devoting time to tires while at the track, then a driver might be muttering this sentiment: "I just don't know what happened. During practice and qualifying we were so fast, but when the race came around we were horrible."

Tires will go through heat cycles, build up air pressure, and then lose air pressure. They will get to their optimum temperature and then cool down. All of these changes can wreak havoc on your setup. One of the biggest mistakes a racer can make is checking air pressure immediately after a race and releasing the built-up air pressure, which is a product of the heat the tire produced. The tire will cool off and the air pressure will eventually go back to its original reading. But when you release air pressure when the tire is hot, it is still going to lose pressure while it is cooling. So, if a driver gets into a bind while working on something underneath the car and it's time for the feature, he may think he has already checked the air pressure when in reality the tires are a few pounds low.

Is there a type of air to put into tires to help with the temperature build-up issue? The answer is yes. Most teams use nitrogen instead of straight air out of a compressor. Nitrogen is more stable and consistent than air, which will contain moisture from the changes in humidity throughout the day, making it very inconsistent.

If you are running air out of a compressor, you will probably be seeing a variety of air pressure buildups. You could make one run and have a five-pound increase and the next time on the track have an eight-pound increase. This is the same reason that airlines use nitrogen in the high pressure tires in small and large aircrafts.

Some teams also fail to realize that temperature and pressure increases will sometimes alter the stagger they are running. Losing a quarter-inch of stagger in the rear of the car will drastically change the way it handles, not to mention changing ride heights, crossweight, left-side weight and front-to-rear weight ratio. It's important that before your tires even hit the track that each one is measured and the measurements are recorded to the 1/16 inch.

Then, after the first run, make sure tire temperatures and air pressures are recorded, both immediately after the run, and after the car cools down and air pressures are back to normal. Then, air pressures should be reset. A pound may have to be removed from a tire or a pound replaced here or there; just make sure that the tire has cooled down before taking air out of it.

After a return to the levels from before the car hit the track, measure the tires again and see if they have grown or shrunk. If they have changed a 1/32 inch or a 1/16 inch, that is an easy fix; put in or take out a couple pounds of air, as needed, and let the tires sit for 10 to 20 minutes. Then, reset the air and measure again, and this should fix the problem.

Top Nextel Cup teams have tire management down to an art form. They not only keep a close eye on air pressures, sizes, and tread depth, but they also check the spring rate of every tire, as each one has its own individual spring rate.

The spring rates of the springs in the car are the measurement of how much pressure it takes to start collapsing the spring at a given point. The tire's spring rate, meanwhile, measures how stiff the sidewall of the tire is at a given pressure. Most of the tires used in Friday or Saturday night races have close to the same spring rate. However, you can see a significant difference between spring rates if the tires are used. Used tires have experienced more heat-cycles and that, along with possible damage to the sidewall, may have reduced the spring rate. This, in turn, will produce a much softer spring rate which will damage the setup you are throwing underneath the car.

Most asphalt tracks are dominated by Goodyear, although there are some asphalt tracks and touring series, including all of the ARCA touring series, that use a Hoosier tire compound.