Brake Caliper Piston "Lips"

[BattleBug]

I'm in the process of rebuilding my brakes and I've an issue with my front caliper pistons. See picture:

Notice the left piston has a lip at the top however the right is "lip-less". I am absolutely positive I marked which was inboard vs outboard. Then I popped the pistons out of the other caliper they were opposite the first with respect to the lip...so my question is: lips in or lips out?? Anyone have a diagram?

Additional question: Any recommendations for brake cylinder lube? Brake fluid? vaseline? wheel bearing grease? EVOO?

Thanks many!!

[ECARRILLO]

No picture

[Tifosi]

<-- can see picture


TBH, I wouldn't be super concerned about the missing lip as pretty much it's only purpose is to hold back the dust boot.

Granted, you'd have to make sure the boot lip didn't get pinched between the piston and a brake pad when swapping things out, but beyond that, it's relatively harmless.

For lube, there is a specific type out there just for that (my book calls it 'bremszylinder pasta' and the call for it on the boot not the seal) though a thin smear of new, clean brake fluid on the seal not the piston should give you enough slip to get the pistons back in their bores.


EDIT:
oh, duh, lemme re-read that again.

Lipless inboard or lipless outboard is the question.

I dunno LOL