These are the rear brake discs from a 1988 Citroën CX 22TRS. The one on the left is extensively worn, with corrosion and pitting. The one on the right is new.

The damage to the left disc was largely due to the brake caliper being stuck. On vehicles with Citroën's hydraulic suspension, the pressure applied to the rear brake is controlled by the pressure in the rear suspension. As the weight increases, so does the brake pressure and therefore the braking force, which helps to keep the car stable. In this case, the car was mostly driven with one or two occupants in the front and no load on the back, so the rear brakes were never exercised.

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