Refurbing calipers - do I use sealant on the piston seal?

[Bennet]

I'm refurbishing some calipers this weekend. (As in, disassemble, clean, reassemble with new rubber bits.)

Haven't done this before. When installing the new rubber seal on the piston, do I need to add sealant of any kind to make sure it seals properly? Some videos mention this, and some don't.

If so, any recommendations for what to use?

[TimmyMallett]

Red rubber grease I thought?

[E-bmw]

It is not a sealant, but yes, as above red rubber grease is generally the go-to assembly lubricant of choice.

[Bennet]

Red rubber grease it is then. Thanks.

[richhead]

you can get special seal conditioning fluid, but dont bother, just leave to soak in brake fluid over night, and never, never, never use grease on brake seals. especially rubber grease........
brake fluid is all the lubricant it needs, why would you use something that it never sees in service., makes no sense. grease also boils way below the temp needed in brakes, causing gas bubbles, not what you want on brakes.
anybody recommending using anything other than seal conditioning fluid or brake fluid on a caliper rebuild, is someone to avoid.

[tux850]

Bigg Red suggest the use of silicone grease or brake fluid. Given you'll always have the latter when doing a job like this it makes for an obvious recommendation.

Edited by tux850 on Monday 1st July 11:15

[littleredrooster]

...and when fitting the seals, make sure you get them the correct way round. Most (all?) have an inner face and an outer face as they are not symmetrical.

[B'stard Child]

richhead said:

you can get special seal conditioning fluid, but dont bother, just leave to soak in brake fluid over night, and never, never, never use grease on brake seals. especially rubber grease........
brake fluid is all the lubricant it needs, why would you use something that it never sees in service., makes no sense. grease also boils way below the temp needed in brakes, causing gas bubbles, not what you want on brakes.
anybody recommending using anything other than seal conditioning fluid or brake fluid on a caliper rebuild, is someone to avoid.

^ that's what I've always done - overnight soak in clean fresh brake fluid

The only time I've used red rubber grease is on the dust boots

[E-bmw]

B'stard Child said:

richhead said:

you can get special seal conditioning fluid, but dont bother, just leave to soak in brake fluid over night, and never, never, never use grease on brake seals. especially rubber grease........
brake fluid is all the lubricant it needs, why would you use something that it never sees in service., makes no sense. grease also boils way below the temp needed in brakes, causing gas bubbles, not what you want on brakes.
anybody recommending using anything other than seal conditioning fluid or brake fluid on a caliper rebuild, is someone to avoid.

^ that's what I've always done - overnight soak in clean fresh brake fluid

The only time I've used red rubber grease is on the dust boots

My mistake, for some reason (even though piston seal was in the title) I was thinking dust boots. My bad!