The pilot stated that he had taken a personal flight around the local area and when he returned about an hour later, he noted that the winds were about 10-13 knots and a crosswind existed for the active runway (runway 28). The landing was normal and as the airspeed slowed the airplane weathervaned and moved towards the edge of the runway. A landing gear tire caught the snow at the runway's edge and the airplane went up on its nose. The pilot stated that the right brake was too mushy to "hold the aircraft with strong cross wind." The pilot also stated that the brakes needed to be maintained better and that he did not realize that the brakes were too soft until it was too late. According to airport personnel the pilot reported a crosswind from the south. As the airplane landed, the airplane began to weathervane, and the pilot activated the right pedal. Airport personnel noted the winds were from 180 degrees at 13 knots. He noted a skid mark on the runway from the right main landing gear tire that began near the centerline. As the airplane continued off the runway, the left main tire went through the snow off the runway edge for about 50 feet before the airplane pivoted and came to rest on its nose. A Federal Aviation Administration (FAA) inspector interviewed the pilot. The pilot stated that he was performing a wheel landing when the airplane weathervaned to the left. The pilot applied right rudder and brake to correct back to centerline, but the right pedal was soft and spongy. After departing the runway, the airplane nosed over, which caused structural damage to the right wing inboard rear spar. The pilot also reported to the FAA inspector that he knew the right brake was soft before takeoff, but decided that it was not an issue at the time as he had made left and right clearing circles on the ground prior to takeoff without any difficulty. The FAA inspector examined the brake system and noted the right brake was "spongy," and that the brake pedal would "bottom out with very little force applied."