Brake housing is (usually) wound so that it doesn't burst under use and make your brakes not work, this also means it compresses slightly in use, that compression means it won't work for gears as they need the cable to move the same amount at the mech as it does at the shifter to index properly.
Much appreciated, I'll pass on the info :)
p.s. the brake canle housing he wants to use is the jagwire elite aluminium 'pearls' one, which is compressionless, would that make a difference?
Brake housing is (usually) wound so that it doesn't burst under use and make your brakes not work, this also means it compresses slightly in use, that compression means it won't work for gears as they need the cable to move the same amount at the mech as it does at the shifter to index properly.