What components must be present on a wheel to ensure safety?

The essential components for ensuring safety on a wheel are studs or nuts. These components are critical because they secure the wheel to the vehicle's hub, allowing it to rotate safely while the vehicle is in motion. If the studs or nuts are not present, loose, or damaged, the wheel could detach, leading to a catastrophic failure while driving, which can result in severe accidents and injuries.

While rims and tires are crucial for the overall operation of the vehicle by providing traction and support, the security of the wheel itself is paramount, which is provided by the studs or nuts. Brake calipers are also important for the vehicle's braking system, but they do not directly influence the attachment or safety of the wheel to the vehicle. Hubcaps, while they may serve a decorative purpose and protect some components of the wheel, are not safety-critical in the same way that wheel studs or nuts are.