Your caliper is hanging up!!!! Heat = expansion, Cold = contraction, remove the caliper, pull both slide pins and inspect them and the boots, clean or replace, then clean the bores out with brake cleaner. Use dielectric grease ( caliper grease) to relube the slide pins and reinstall. I would also replace the pads on both sides. Hawks LTS or Friction Performance from AZ are good pads, you need to change both sides!!! There is no way you rear rotor should be that hot, the only thing that builds that kind of heat is friction!!! Your fronts do 90% of the braking and even they don't get "spit sizzl'in" hot under normal use. This should fix your problem. I would also have both rotors turned while they are out. You can't eye ball warpage.
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