Last spring, the NASCAR Sprint Cup teams were plagued with left-side tire issues at Auto Club Speedway. Many drivers — including Jimmie Johnson and Jeff Gordon — pointed a finger at tire manufacturer Goodyear.
Because each track is unique, NASCAR and Goodyear work together to determine the best tires for each track. Goodyear’s experts must find a way to balance the necessary strength and durability with the track grip the teams need. The key is to choose the best tire compounds for each surface. The softer the tire, the better the car grips the race track. Soft tires, however, wear out much faster.
New Tire Compound for Left Side Tires
Through an October 2014 testing session, Goodyear engineers determined a new compound should be used to increase left-side grip at the track. The tires are also slightly different in construction than last year’s model. At Fontana this weekend, both the Sprint Cup and Xfinity Series are running the same Goodyear Eagle Speedway Radials. This is the fourth year the right side tires (code D-4408) have been run at Auto Club Speedway, and the first time teams will be using the left side compound (code D-4636).
Teams used to buy tires from Goodyear each week, but since 2006 a limited number of tires have been offered to each team through a lease program. At the end of the weekend, all tires are returned to Goodyear for recycling. This weekend, the Sprint Cup teams will be allowed five sets of tires on Friday and Saturday, and 12 sets for Sunday. The Xfinity teams will use only 8 sets.
The Role of Tire Circumference and Inflation
All NASCAR oval track races use left side tires that are slightly smaller in circumference than the right side tires. This makes it easier for the driver to turn the car left, and makes the entrance into the corner smoother.
This holds true for this weekend’s race at Auto Club Speedway. The left side tires are slightly smaller than the right side, at a circumference of 87.56 inches versus 88.43 inches. The right side tires are also typically inflated much more than the left. At Fontana, the minimum inflations recommended by Goodyear are 22 psi on the left front and 20 psi on the left rear. By comparison, the right front must be inflated to at least 45 psi while the right rear should be at or above 42 psi.
At almost every track, teams will start the race with low tire pressures. This is because the pressure will build during a long green flag run, and inflating the tires too much hinders their ability to grip the track. Tires used in qualifying, by contrast, will typically have higher air pressures from the start.
While low pressures can cause some issues, staying within the recommended guidelines should keep teams out of trouble. Many won’t however, because there is a competitive advantage to be gained in a sport where templates and other regulations have taken away many ways teams traditionally gained on their competitors.
Will the new left side tire help at Fontana? While tests with the new compound last fall seemed promising, there’s really no way to be certain until the cars hit the track.NASCAR Sprint Cup drivers will take the green flag for the Auto Club 500 at 3:46 p.m./et. Pre-race coverage will begin on Fox at 3 p.m.