Rear calliper pistons

Had a new tyre fitted last week, so taken the opportunity to give the calliper a clean. 2 things I noticed. 1, only one piston moves when pressure is applied. When I block this piston, the other one then moves, is this normal. 2 the pistons are not shiny like I have seen on YouTube videos, albeit different brands of brakes. Are the Grisos usually shiny, ie stainless steel or are they made from something else

Also, the spring. It fell out when I removed the pin, no can’t remember where it goes. The only logical place is it sits on top of the pads (when calliper is in position) at the pin end?

Don’t like to bump, but can anyone provide assistance?

Sorry, I'll check on a spare today. It should be fairly self evident I think.

It's normal for only one piston to move when there's no resistance. One will have less "stiction", so will move.

I am pretty sure that the pistons are grey and if they are "free" then by holding a finger on one piston will allow the other piston to move and you should be able to push them back with your fingers.

If not they need a clean and rubber grease.

This may apply to GRiSO's - The metal spring plate - if you turn the caliper on its back (so to speak) there is a ridge that it locate onto, you tend to get a lot of road debris clogging this up [so clean before refitting]

Thank you Pete, Brian and Rick. As always on this forum, got the answers. Here is a photo of the spring position. Hopefully this is right? Only logical place it could go. I assume purpose of to allow the pads to move slightly within the calliper under load. [You must be registered and logged in to see this image.]

Hi, just want to check the above rear calliper assembly was correct?