One problem related to brake disc has been reported for the 1999 Ford F-550. The most recently reported issues are listed below.
Rear disc brake on driver side rear, extreme wear of rotor because of Ford engineering problem. Caliper is located on front of rotor, preventing mud, sand and gravel from self cleaning from rotor. Caliper acts as trap to hold debris against rotor, causing severe deterioration of rotors, including wear into cooling web and seperation of rotor disk from hub. Opposite rotor shows very little wear. Also caliper mounted on front of rotor traps gravel between pads and caliper frame, preventing pads from releasing. This brake problem has occurred now three times in less than one year on this 1999 f550, and three times on our 1999 f450. This brake problem is a severe traffic hazard in the fact that the disc pad can wear into the rotor web, and upon application of brakes at high speed could cause the driver side rear wheel to lock, possibly causing a severe lane change into oncoming traffic. Disc pads should be mounted on rear of rotor so that forward motion of wheels would enable self cleaning.