I still dont understand why the 70 US spec was single disc ? wonder how effective the brakes are compaired to the UK/Euro twin disc.
Lou, the standard configuration for all single single shock R65s (except LS) sod in Australia was single disc.
The wife's became a twin ATE when a friend was going to Germany and was tasked to buy the accessory kit from BMW to fit a 2nd disc. I have always regarded her R65 (R65/80) as being "adequately" braked in both single and dual disc lives, in fact if I had an option at all I would probably have said of the twin disc arrangement "good brakes, but wooden".
I have never really felt concerned about the single disc that was fitted to my 1984 R65, again my thinking was that it was not the best brake in the business (especially compared to the GSA), but that it supplied adequate braking.
I should fess up here that my R65 had a very long lever due to an absurdly long brake hose that I had to loop over the rear of the headlight - the long lever beign the result of air trapped in it that I never bothered to eliminate as I was always going to fit a better hose just as soon as I go a round to-it.
Then in the last few weeks I fitted a K100RS front end to the the R65 and the collateral damage to that was twin Brembo calipers (I also own a set of Brembo 4-spots but couldn't justify the cost of the inevitable new master cylinder).
Well, the combination of HEL stainless lines and retaining the 12mm master cylinder has opened previously undreamed of levels of braking power.
On a recent ride I amused the members of my club by performing "stoppies" on a particularly sticky stretch of bitumen, there are photos of the back wheel nearly three feet off the ground. I abandoned that fun and games as I started thinking about the unfair strains on head stem bearings, frame and the general wear and tear of the rear wheel slamming back down onto the ground. But the point was that the R65 is now almost absurdly over-braked, I can easily lock the front wheel with a single finger curled around the lever. It's not dangerous in my view, nut it is something that will take a while to adjust to.
I didn't bother to measure the piston size int he ex-K100 calipers, they pressed home without any great pressure and expelled fairly clean fluid, so I decided to simply use them as-is and see how they go. I do not think that whatever the hydraulic ratio is that I've ended up with would have worked with "rubber" hoses, only the unyielding nature of braided steel lets it work.
