SR22 pilot reports a brake fire after a very long taxi to the run up pad. A dragging brake was thought to be responsible as the aircraft was parked outside in January and was cold soaked.

Narrative

Plane was out over night (no room in hangar) and thus cold soaked in January. Taxi felt normal; plane usually requires a little brake pressure to taxi straight when in a cross wind situation. Upon reaching runway; a run up was begun. As the engine RPM increased the plane moved forward slightly. The right brake felt stiff so extra force was applied to possibly loosen it up. The right brake popped and went to the floor. Then the plane pivoted on its left tire and turned 180 degrees. As the plane turned due to loss of the right brake the engine was shut down to keep from moving any further. Tower was notified of situation. Then smoke was seen from under the right wing. Again; Tower was notified. Both occupants then exited the secured airplane. The pilot used the on board fire extinguisher and tried to subdue the flames to no avail. A guess as to why this happened; the right brake froze due to the sub freezing temperature causing the pads to rub the brake rotor. Due to the extended taxi (over a mile) the rotor got extremely hot and failed; causing the fire.