Is this brake piston fully compressed?

[exanVZ]

Changed rotors and pads and can't get the caliper over the new pads. Not able to compress the piston any further, have tried clamps and have opened the bleeder, even tried taking the caliper off completely to make sure there was no pressure preventing it from going further back in. It's the exact same on both sides and the piston does move normally when I pump the brakes, and compresses back to the same point so I don't think it's seized or damaged.

Seems to be about 1mm too thick so either my pads are too thick or the piston needs to go further back in.
The ute has the PBR brakes same as a monaro and SSZ.

Using DBA2021S rotors and Bendix DB1332 pads which all match up with my car (VZ ute).
These are 18mm rotors (correct size) so could these pads be for 16mm rotors?

Pics below, what do you think? Wrong pads or piston issue?

Edit:
Looking up specs online, bendix says 114x58x18mm (L x W x D) and comparing to EBC red or yellow it's 114x58x17mm which would make up the difference in size for the 18mm rotor vs 16mm rotor on other commodore rear brakes although bendix specifically list this as compatible with vz thunder/mondaro/ssz/commodore

 

[hademall]

Did you take the cap off the master cylinder?

 

[exanVZ]

Did you take the cap off the master cylinder?

Yup it's open.

I'm a bit fed up with this job, so I did something possibly dumb and lightly sanded 0.1-0.2mm off each pad until it barely fit and put it all back together. Brakes might be tight until it wears in, it's only the rear brakes so slightly less concerned about doing this than with the fronts (which hopefully won't have the same issue).

 

[greenacc]

It could be a few things I guess, even the rubber backing on the pads. Did you include the rubber thickness in your measurement?
As long as it drives ok now I guess. Mostly depends on how evenly you rubbed them back ie hopefully flat rather than wonky.

 

[exanVZ]

I just sanded them with even pressure on a square of sandpaper flat on my bench so I hope it should be pretty even. Only really took off about 0.1 to 0.2mm, I have some calipers so I was able to check the thickness of each pad and tried to get them all about the same.

Went out for a drive tonight to break everything in and everything seems sweet so hopefully all good.