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I have taken apart an older Shimano 105 brake calliper, there are tiny bearings that sit inside the piece of plastic as shown in the image. Is 'standard' teflon bike grease appropriate here, or should silicone grease be used. As I understand it, the chemical composition of certain grease can cause degradation to plastic over time. I know that silicone is good for plastic, but is it good to use with bearings?

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It is my belief that this fear is overstated, and I'd simply use Park polylube. (I've seen threads where boat mechanics discuss using their favorite marine grease on all their bike parts with no ill effects.) If worried and wanting to spend more, I'd use suspension grease, which is by definition going on plastic/rubber seals. A couple of the more popular name-brand suspension greases are just Slickoleum, re-packaged and marked up 3-4x in price. You can get a tube of slickoleum for around $12, or a bigger tub to last your whole life for around $20.

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  • I've used the same tub of marine grease for just about everything for 10 years (about 15% of the way through it) and no complaints so far. Smells, feels, and looks eerily similar to Phil Wood's grease. – Paul H Jul 8 '19 at 21:08
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    To address the silicone bit, it's my understanding that it isn't great for higher-stress uses like ball bearings, but that's presuming ball bearings in a fast spin situation, I believe. I'm sure it would handle the lower-speed, lower frequency use in the brake, but unless it was really thick stuff, it will probably migrate out. I've got super-thick pure silicone I use for mixing treadmill lube, and even it won't stay put like a regular bike or marine grease. – WPNoviceCoder Jul 9 '19 at 21:09
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Plastics endure grease fine - many greases come in plastic tubs or tubes.

You've mixed plastic with rubber - there are many specific requirements around rubber and lubricants.

Given its in a brake caliper, you want a lubricant that won't risk migrating out to the brake surfaces.

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