BMW has used similar calipers for many non-M models for a long time that use a headless pin with smaller diameter threads that goes through a rubber bushing mounted in the caliper. It may be an ATE caliper, and similar calipers are used on many VW and Audi cars. My Bentley BMW service manual says no lube is to be applied to the pins during assembly. I got new ATE bushings and the instructions that came with them said to lube the outside of the bushings with silicone grease for installation, but said nothing about lube on the pins or inside of the bushings. Very rare situation to have caliper pins with no lube, and I have been contemplating why not. Looking at the ribs inside the bushings where the pin rides, I concluded no lube is specified because they want the bushing to dampen, and not to slide. I have heard that caliper pistons during normal brake applications don't slide, but just deflect and that the seal assists in the piston returning when pressure is released. ATE may have designed the caliper pins to function in a similar manner as the piston seal during brake activation. I now think no lube is specified because they want the pin to stick to the bushing, or at least to the ribs in the bushing. Do you apply lube to the pins on these type of caliper pins?