slightly used stock front wheel/rotors install problem

[Jayspeed]

I have stock original front wheel/rotors that I swap with another factory front stock wheel/rotors setup(bought used and barely used). The problem is when I go to put on my spare wheel, my calipers won't fit on the rotors unless I compress the pistons into the calipers. Whats happening is I'll slide the caliper onto the disk and the caliper would then need to be brought outward away from the wheel in order to slip onto the mounting points. Basically, the inner pistons would need to be compressed in order for the caliper to slip on. You know that noise sintered pads make? Well, I hear that while riding now without applying the brakes. Could this be that the rotors that came with my wheels are not as worn as my originals? We're only talking a year old here. It seems the rotors are a few mm's outward from the center of the wheel than my original stock ones.

[loridin64]

make sure you have your spacers on the proper sides. I recently swapped out my rear and swapped the spacers on each side by accident. Same thing was happening to my caliper...

[Jayspeed]

make sure you have your spacers on the proper sides. I recently swapped out my rear and swapped the spacers on each side by accident. Same thing was happening to my caliper...

Yep, checked that.

[loridin64]

are there spacers behind the rotors as well? You mentioned that they are a few mm's outward. I wouldnt think that a few mm's would make that much of a difference with all the play that the calipers have.
is it a contant noise? could the calipers be bent or just not mounted straight?