BMW caliper pins, no lube?

Messages
1,200
Location
Missouri
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?
 
Messages
15,120
Location
Upper Midwest
No I don't. My old BMW has the same type of pins and boots and the BMW service manual says to leave them dry, which I have always done. It has been fine up here in the Wisconsin salt belt.
 
Messages
915
Location
California
I have never put lubricant on any of my BMW's guide line. VW has also been saying not to lubricate the guide pins. It's to prevent gumming up due to the lube getting contaminated with dirt. The guide bushings are made from a very smooth elastomer and I don't see any benefit to using lubricant on bushings and pins that are in good shape. I do however replace the bushings every time I replace the pads.
 
Messages
9,373
Location
Canuck living in California
My 2006 mazda 3 has the same design ATE calipers and I lube the pins. 14 years later I'm still on original bushings up front. I replaced the ones in the rear because I thought they got swollen, but it turned out to be something else. Either way, it probably matters little in the grand scheme of things.
 
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Messages
4,117
Location
SW Ohio
If the automaker is saying it's not needed, it's really probably not needed. Yes, they evaluate everything, from the cost of lube to the labor needed to apply it too and if they can save those costs for something unnecessary, they will. That said, it doesn't mean you should not apply it or that it will cause problems.
 
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