AUGUST 2018 ISSUE
Have you ever wondered how pit crews in racing are able to change four tires in such a short amount of time? Unlike your typical Lexus passenger car that requires five lug nuts to secure each of its tires, the RC F GT3 race car is equipped with a single ‘wheel nut’ to ensure each of its all four wheels and tires are replaced and securely fastened as quickly as possible during a pit stop.
The wheel nut on the RC F GT3 is circular and requires the use of special sockets, and when put on the race car it needs to be extremely tight because of the flexural loads on the wheel. You will see from the picture that there is a cone located in the center of the wheel nut, which helps center the wheel because it is very important for a wheel to be concentric with the hub that it’s mounted to. If it’s not concentric with the hub, the wheel will not rotate correctly and the driver will experience a very bumpy ride around the race track. The wheel is very carefully located and the cone helps centralize the wheel to ensure it fits properly into place and in addition, there are drive pegs located on the mounting surface of the wheel, which mate with the hub to ensure that both acceleration and braking torques are catered for.
The tire changer on pit lane completes this process by using a ‘wheel gun.’ The tire changer uses this very large socket to assist in engaging the wheel nut to quickly replace and then tighten the new wheel on the car. These guns are multi-directional depending on which side of the car the tire changer is working on. The wheel gun includes magnets built into the socket, which hold the wheel nut in the socket when the tire changer removes it. The other mechanic puts the new wheel on, fitting the wheel nut concisely before tightening it up. Once the wheel nut is securely tightened, he pulls the gun away and the magnets separate and the Lexus heads quickly back on the race track.
Fast pit stops are a key to success in racing and the use of wheel nuts and wheel guns are essential to not only a quick pit stop, but also to ensure that the tires are properly secured and tightened on the RC F GT3.
