A benefit is that they tend to be self-cleaning i.e. they wipe the braking surface as they are applied. A drum brake has the potential of filling with water and mud and are less easy to inspect. Ever had a drum fill with water and freeze overnight? Sister's old VW bug didn't have the clutch to break it free so BiL would have to heat up the drums to loosen them in the AMsWhy do you want rear disc brakes?