Need to take brake disc off wheel, without damaging it. (NO PICS)

I have a set of R33 wheels that I'm thinking of using on my Silvai, but one of the brake discs is glued to the rim from behing. I tried pulling it off but the center of the wheel goes with it and the wheel will break before the disc comes off. Brake fluid makes glue very weadk and it can be taken off easily like this but here;s the big problem... the wheel has a very nice color to it and I don't wan that color coming off becuase of the brake fluid. So I need your help guys, I need to somehow make the disc come off. I also tried cutting from behing with a blade, did'nt work. PLEASE HELP!!!

ive heard that if u want glued pieces to come apart easily, put the piece in a plastic container and put it in the FREEZER for a few hours, the cold will make the glue brittle and shoudl come off easy, and i dont think it will damage the wheel ;)