Brembo 4-piston caliper has 38mm diameter pistons
You might find it easiest to fit a master cylinder with a larger bore. Increasing the bore of the master cylinder while retaining the stock sized caliper would increase the PSI at the caliper.
Of course, doing that would most certainly require the stainless hose recommended by TwoJugs.
I bought a $35 master cylinder on eBay and an 02 r6 caliper for $20. Had to file the caliper a little on the inside to fit the factory rotor and had to grind the backside of the caliper a little to clear the spokes. Made a bracket template and had someone mill it out of 1/2" aluminum (Brother in law did it for nothing!) Put on a stainless line and it works amazing. All for about $70. 3/8" aluminum would have worked but he had 1/2" for free so....
This is on my 76 btw.
Pandemonium Choppers kit $36 and brembo caliper (2 pin style) from a Ducati with a stock rotor work great! Just make sure you match it with the proper master cylinder. I use this kit on both my XS's with the magura master that MikesXS sells and the stopping power is like a modern
sportbike.
View attachment 288528
View attachment 288529
My setup is a 320 mm custom made ISR disc, 5 mm thick, offset 23 mm (measured from OUTSIDE of disc friction surface to mounting surface) Brembo 4 piston caliper with 65 mm C-C mounting holes. Spoked stock XS wheel. No filing requiredHi there, I know it has been like a decade lol however if you’re still here and you remember …that pandemonium brembo set up of yours, did you have to file off the back of the caliper to clear the spokes?
I’ve heard and read a mixed bag regarding the fitment of these.
I have used early Triumph calipers also, they work very well. Off topic but nice 500!This is the pandemonium kit and brembo on the left side of a XS front end, it looks pretty clean but you have to hack up the caliper a little:
View attachment 317503
Chris
Oakland, Ca.