If I were upgrading the front brakes for the sake of better braking I would approach the project as if I were improving an entire system. I would first eliminate anything that I believed detracted from maximum braking. As I have mentioned before, the position of the lower link can increase or decrease the effective braking. If the link is parallel to the road (or lower) the braking is 100%. If the eccentrics are riding higher than that, the braking is probably 25-35% less effective, no matter what brakes you have. Replacing stock brakes with discs will lead mostly to much easier ineffective braking. I believe that TT mentioned applying the disc brakes on a Vincent and watching as the fork went from laden to full extension. Does the bike slow? Yes, but it is also involved in a lot of non-compliant behavior that erodes good braking traction. The discs will enhance or exaggerate the action, but it will not abate it.
In choosing the calipers and discs, I would select a flat disc. This will allow the carrier for the disc to be a very simple design that is easily turned up quickly on a lathe. You will probably choose the discs and calipers together. For a twin I would go with 11-12" and at least a two piston caliper. Whatever is easily available at the breakers, but still supported by the manufacturer. I think a large disc works better on a large wheel providing a much better rim to brake leverage ratio.
For the master cylinder I would use the unit that was available as stock. I would not use the BMW unit because at this point I feel it would be honoring style more than form. Justin had an issue with mounting the master cylinder on the Prince because of the lack of room between the handlebars and cowl so an alternative was used. I found a radial master cylinder that worked really well and and it provided him with what he desired, but the mechanical pairing must be done. With a matched system you can be really lazy and end up with a wonderful brake.
This is similar to the approach taken with Sam's brakes and they have proved to be wildly successful. I think he paid $100 for all the parts on Ebay and he used the 14" springs. You can see the attitude of the lower link in the photo.
Best of luck,
David
In choosing the calipers and discs, I would select a flat disc. This will allow the carrier for the disc to be a very simple design that is easily turned up quickly on a lathe. You will probably choose the discs and calipers together. For a twin I would go with 11-12" and at least a two piston caliper. Whatever is easily available at the breakers, but still supported by the manufacturer. I think a large disc works better on a large wheel providing a much better rim to brake leverage ratio.
For the master cylinder I would use the unit that was available as stock. I would not use the BMW unit because at this point I feel it would be honoring style more than form. Justin had an issue with mounting the master cylinder on the Prince because of the lack of room between the handlebars and cowl so an alternative was used. I found a radial master cylinder that worked really well and and it provided him with what he desired, but the mechanical pairing must be done. With a matched system you can be really lazy and end up with a wonderful brake.
This is similar to the approach taken with Sam's brakes and they have proved to be wildly successful. I think he paid $100 for all the parts on Ebay and he used the 14" springs. You can see the attitude of the lower link in the photo.
Best of luck,
David