Hi Alan,
The first brakes I had on my Morgen were mechanical disc brakes from a bike. 180-200 mm if I remember correctly. They were quite capable of stopping from full speed once, but were quickly rendered useless on downhill roads, because of the very low heat capacity of the actual disc. If you ever drove a first generation Austin Mini-Cooper with disc brakes, you know how great they stopped once, and how quickly they faded with each additional application. The discs simply did not have enough mass and cooling capacity to keep the pads from over heating. I'll admit to being a fanatic about braking performance. Old Fords and Austins taught me about bad brakes, and a ride in a racing XKE taught me how great brakes can perform.
The hydraulic system I found was purchased from an ATV parts vendor, but were labeled as being for a scooter. My guess is that they are generic parts and only the hoses make them fit a particular vehicle. The thing I really liked about them was the fact that they cost much less than the bike parts, and worked so much better.
TTFN,
Dennis
