Originally Posted by
RubeRad
Seems like you answered your own question; fat (5mm) is for brakes, thin (4mm) is for shifters. Brake cable is spiral-wound metal, and stronger for saftey, shifter cable is a bundle of straight wires, "compressionless" for shifting precision.
Not really. I just replaced my shift cables and noticed that the new Jagwire shift housing was significantly thicker than the old Jagwire shift housing. The new one fit the ferrules snugly, the old one was loose. Neither one is spiral-wound, both housings use apparently identical straight bundles. I may not understand what I saw and would appreciate an education...