Since having written on this thread and having seen the ridiculous prices people are asking for GT550 suzy brakes (enough to buy a proper replica robinson 4ls), I went with a Triumph TLS for my project special instead.
Now I have it in mind to buy a G15 CS when one pops up and the only thing I think I will want to totally swap out will be the front brake, I just want more stopping power than the Norton hub can give (even with stiffener kits etc.) and I refuse to go for Suzy brake because it is overpriced and two heavy imo.
So I decided to think outside the box given some of the ideas in this thread and embark on an ambitious project.
Acotrel I checked out this idea for a doubling up a Triumph half hub, indeed these are twinned 8" Triumph brake from a T110 (amongst other models).
I've managed to acquire two such hubs but only one brake plate for much less than a Gt550 drum, they've yet to arrive in the post as they are coming from abroad.
My idea is to bolt the two hubs up back to back, this will enable me to make some holes in each hub to lighten the drums without exposing them to the wet and rain. My next objective would be to find a set of plain brake plates without vents that would fit the half drums, I imagine Norton or Triumph 8" SLS brake plates of some kind, finally I would like to convert these SLS brakes to TLS.
I've calculated the performance of such a brake given surface area, shoe width etc. and it should be even in dual SLS form superior to a GT550 drum, the weight if I drill it should come under a GT550 also.
This kind of setup would tick all my boxes, nice looking plain 4ls with no vents (not a race bike so such cooling is not necessary anyhow).
Having said all this, am I mad or does this sound like a good idea? Anyone know of any issues I may come up against that I'm not aware of?
Only the backing plates will give you a problem. You need right and left hand ones. For a road bike I'd even use SLS items - probably be enough. You might find you can buy Grimeca TLS backing plates at a reasonable price. BSA backing plates might be adequate for your purposes, you should not need the air scoop.
That '57 Triumph is a lovely old bike. I used to own that model thunderbird, it was a really great bike. I was always a bit apprehensive about it, because someone had been killed on it in a road accident.