My guess would be that (one) you probably have zerks to lube your wheel bearings
(two) you keep them well lubricated
(three) that they may easily be OVER lubricated causing grease to get onto the braking serface. The HEAT is most likely from the brakes trying to operate on a greased surface.
Lube the wheel bearings only about one squirt each season (unless you have signs of leaking grease, in which case fix the leak) and make sure your brakes are correctly adjusted and CLEAN (no grease in the drum) and no brake dust inside the drum.
Good luck / Skip