What is a common reason for rust appearing on your wheels?

Rust on your wheels can often be attributed to various factors related to the vehicle's components and their condition, particularly the lug nuts. When lug nuts begin to rust, they can release particles that become visible on the wheel surface, leading to spots of rust. This situation commonly arises in wet or salty environments where moisture can cause metal surfaces to deteriorate over time.

Each of the other choices mentions potential contributors to rust, but focusing primarily on the relationship between the lug nuts and wheel rust emphasizes that as they oxidize, they can effectively 'spit' or shed rust particles onto the wheels. While old wheels and brakes can also contribute to rust formation, the direct action of rusting lug nuts provides a clear and common reason for what one might observe at the wheel's appearance.