I understand BMW says not to. It seems that other automakers that use the same ATE brakes do use lubricant on the slide pins as well as ATE themselves market a caliper grease that they say can be used on slide pins. Their system does appear to encapsulate the slide pins 100% so the risk of moisture (causing rust) or contaminants getting in there is pretty minimal but there's really no harm in applying lubrication either.
The commonly available
ATE Plastilube is meant for metal-to-metal contact points on the ears of the pad, as well as the backs. (BMW also used to sell smaller packets of it under their own label, and nowhere in the FSM have I ever come across has it been specified for use other than on hard points, or in conflict with their dry pin edict.)
But is is not rubber safe (tube says "
nor to rubber parts"), and therefore not suitable for the majority of standard floating calipers that use rubber encapsulation bushings for the guide pins, nor for the piston seals when doing a rebuild.
ATE makes
a different product ("
Bremszylinder-paste") for that, but it's not as widely available and more difficult to source in the U.S.
Unfortunately, even a reputable parts house like FCP, and others, are spreading misinformation in selling it as a caliper pin lube. The labeling on the back of the tube is very clear. But ATE's
North American page does themselves no favors when it mentions caliper pins in their pitch. Trust the tube, or the marketing?
That said, I will confess that I have gone against guidelines before, and used Sil-Glyde on BMW caliper pins, thinking that there would be no harm. To the contrary, I found that as it aged, it gummed up, and resulted in
increased friction, the opposite of the desired effect. Lesson learned, and the limitations of the product exposed.
