What causes the clunk sound when starting with rusty brake discs?

[MacAdrian]

Here are the reasons for noise from rusty brake discs: Slight rust on the brake disc surface: It can be removed by continuous braking while driving, and no special treatment is needed because minor rust on the brake discs will be worn off during braking. If the rust is more severe, it may cause vibration or shaking during braking, such as brake pad vibration, steering wheel vibration or shaking, or body vibration. Of course, this is under the premise of ensuring safety and not affecting public traffic. While driving, lightly apply the brakes to let the friction between the brake pads and the discs "polish" the surface. Severe rust on the brake discs: When there is significant rust, it can cause unevenness on the brake disc surface, leading to body vibration during braking. The driver can clearly feel abnormalities in the brake pedal, steering wheel, and body. In this case, it will be difficult to remove the rust, and even if it is forcibly "polished," it will still cause abnormal wear on the brake pads and continued vibration. Therefore, it is necessary to perform maintenance on the brake discs every two months to prevent excessive rust development.