We’ve heard a lot, especially this week at Richmond, about tire wear. A lot of right front tires were wearing excessively. As seems to be usual at this point, teams would like Goodyear to use a stronger tire and Goodyear would like teams to dial back their setups, especially their camber.
Camber is the tilt of the wheels relative to the vertical. If the top of the wheel is father out (away from the car’s centerline) then the bottom, it’s called positive camber. If the top of the wheel is closer than the bottom, it’s negative camber.
On oval tracks where all the turns are left, they use negative camber on the right wheel and positive camber on the left.
NASCAR opened up the range of allowed cambers on the Gen-6 car. In 2013, the front wheels could have up to 9 degrees camber and the rear wheels 3.5 degrees. Clint Bowyer even tweeted about having blown the setup by being over agressive.
Although this makes turning easier, it means that the cars are riding on the edges of their tires when they’re not turning. See how the inside of the right tire is the lower part?
The camber isn’t the only issue. When you change direction, brake or accelerate, the car shifts (called load transfer). When you turn left, the load shifts right. When you brake, it shifts forward. So if you brake hard while turning left, or if you have a suspension setup that allows a lot of shifting, you’re going to put a big load on the right-front tire and that also stresses the tire.
Goodyear used their dual-tread tire on the right-side tires at Richmond, where the rightmost ten inches are softer rubber and the innermost two inches are harder – but they were still having problems with cording on those inner edges of the right front tires.
Stu Grant, Goodyear’s General Manager of Global Race Tires, noted that “the operating window between acceptable wear on the right front and unacceptable wear is pretty small.” Tires seemed to do fine up to a point, and then went catastrophically.
While Goodyear’s decided they’re going to look at the tire wear before this Fall’s Richmond Race (which will have a lot on the line), the teams are also going to have to do some set-up searching and decide how much of a risk they want to take with high levels of camber.
The larger wheels and low profile of the tires makes the problem with tire wear worse