Originally Posted by Stephen
I'm sure there are several Brembo calipers that could be adapted to the G/S. You'll have to match up the mounting holes, the alignment with the disc, and the master cylinder diameter. You'll also have to make sure the inside of the caliper clears the spokes.
Now, remember I've only piloted a G/S a few hundred miles...I certainly was not overwhelmed by the stopping power. It did seem to me, though, that the front brake was nevertheless capable of overwhelming the front tire--and the front forks. Better forks will transfer more weight more securely to the front, and improve braking. I've found that Galfer Green pads work extremely well, giving much more feel if not more absolute power. You might also consider a different master cylinder. The no-name on my KLR is a much better piece of equipment than the Magura on my old GS ever was.
I always found airhead drum rear brakes to be near worthless. Judging from the results my pal obtained with his R69, it might be worth a chat with Michael Morse at Vintage Brake
in Sonora to see what he could do.
I guess my real point here is that there are many ways to make the old beast stop better, feel better.
You are correct, starting with the basics is always good. A rebuild of the stock caliper, checking your disk surface is ok and some quality decent pads will provide as much braking that the stock forks even with uprated springs etc can cope with. Adding a fork brace helps a lot and I'd imagine some of the beefy aftermarket top fork clamps will help too. The stock bit of tin does little.