As you can see in the picture below, the disc is rusted only on the inside part and the outer edges dont have rust. I heard discs rust but after braking the rust surface goes away from friction and heat, why is the outer disc clean here in this picture but the inner parts arent? Is the caliper not clamping the disc enough on the innert parts of the disc? enter image description here

Also found another picture where there is rust in middle parts only with majority of the rest of the disc being clean, both of the cars are bmw m4 by the way. enter image description here

1 Answer 1


The rust is caused because the brake pad isn't touching it there. It is plainly that simple. It could be there is a worn spot in the brake pad or in the rotor for whatever reason. Either way, where it is rusty, the pad isn't touching the rotor.

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