Wheels T6.3.1 The wheels of the car must be 203.2 mm (8.0 inches) or more in diameter.
T6.3.2 Any wheel mounting system that uses a single retaining nut must incorporate a device to retain the nut and the wheel in the event that the nut loosens. A second nut (“jam nut”) does not meet these requirements.
T6.3.3 Standard wheel lug bolts are considered engineering fasteners and any modification will be subject to extra scrutiny during technical inspection. Teams using modified lug bolts or custom designs will be required to provide proof that good engineering practices have been followed in their design.
T6.3.4 Aluminum wheel nuts may be used, but they must be hard anodized and in pristine condition