XJ550 Maxim Caliper Rebuild

Hey, y'all. Just a quick questions on brake caliper rebuilds:
Does the flat side of the piston or the "cup" side of the piston go against the pads? When I pulled it apart, the flat side was against the pads and the cup side was in the caliper. The piston on just about every other caliper I've seen has the cup side interfacing with the pads, so I'm thinking somebody has rebuilt this before me and put it in backwards. Is that a correct assumption?

 

If I am reading correctly, the piston was installed incorrectly.

Installed backwards would require a lot of brake fluid to fill up.

 

Here is a random image I found showing proper installation of the piston:

 

Maybe the piston had corroded around the seal area and they flipped it as a last ditch band-aid ? I've seen stranger stuff. Probably have done stranger stuff myself...

 

Your car brake pistons also install open side to pad.

 

Thanks everybody. Looking at Dan’s picture, somebody definitely had swapped it around at some point. Whether on accident or for a reason, I’m not sure. I’ll install it correctly this time.

 

Thinking about it, you’d probably have a tough time bleeding all of the air out of the brakes with it installed backwards. Gives a lot of extra space for an air bubble to get stuck.

 

Yes!