Brake callipers are one of the key elements of the braking system. They are exposed to moisture, contamination and temperature changes, as a result of which they wear. If this is the case, you should consider having them reconditioned, which is much cheaper than changing them, especially that after reconditioning they have exactly the same parameters as new ones. Reconditioning of brake callipers consists in changing only their moving components as the callipers themselves don't wear.