Hmm! Thanks for your replies guys
The way I see it is:
The smaller the bore the higher the pressure that can be applied. The bigger the bore the higher the volume that can be moved 'but at the expense of the pressure' (hence a stiletto heel sinks instantly in the grass and a balloon tyre rides easily over the top).
The complication comes when adding either a second caliper or a larger capacity caliper (holds more fluid than the original) or both.
This is where I think the big square Brembo caliper from the 100R and early 1100 models falls down. I think this caliper physically holds almost double the amount of fluid the original holds (this is in the caliper it's self, not including the brake line and master cilinder) as it is double sided and has four pistons. Hence my thoughts about the 650gs caliper as it is one sided, yet extremely efficient in comparison.
I'm thinking 'as Proff suggests' that because of the larger fluid capacity in the bigger caliper 'or when fitting a second disc' I'll theoretically need to fit a bigger master cylinder in order to move the greater volume of fluid into the caliper/s.
However the greater volume of fluid will inevitably lead to less pressure, leading in turn to spongy and by virtue, inefficient brakes.
So by my thinking, what is needed is a caliper that is designed much better than the square Brembo, that makes more officiant use of it's fluid capacity. Preferably one that fits the fork mountings too.
Val.
. EG standard 14mm with twin discs added goes right back to handlebars.
).
