Motorcycle disc brakes using conventional organic pad materials can exhibit performance unpredictability in wet weather. Testing under controlled dynamometer conditions indicates that the problem arises due to hydrodynamic effects. Braking torque, in the presence of water on the disc, behaves as if pad/disc friction is negatively speed conscious. In extreme conditions effective braking may not occur until near zero speed. Sharp cut off of water delivery gives substantially instantaneous recovery to dry performance.A theorised explanation of wet behaviour of conventional materials has aided formulation and testing of sintered metal materials as a solution to the problem.