Doing a little math to figure out brake master cylinder size

[surfish95747]

Okay guys, I decided to really try to understand the different brake to master cylinder ratios when applied to motorcycles. I have found this chart and some equations and wanted to run them by you guys to see if I was looking at this correctly.

This is the ratio chart from VintageBrake.com



So, according to this chart, I will need to find the total surface area of each active piston on my caliper. I have 4 active pistons on each caliper and I have 2 calipers from a 2005 Yamaha R1.





So the surface area of my pistons in one caliper is 2,550.34mm (four pistons). So for dual calipers, that would be a surface area of 5,100.68mm. So to get the correct ratio results I divide the total caliper piston surface area by the surface area of the master cylinder piston. I compared both a 5/8" (15.875mm) piston master cylinder and a 19mm piston master cylinder. 5100.68/198.05= 25.75:1 ratio (5/8') and 5100.68/283.53= 17.98:1 ratio (which the 19mm piston is the Brembo RCS which can adjust the lever between 18mm and 20mm to adjust feel).

Am I reading this chart right and calculating everything right? The chart says the surface area of active pistons, so I assume that means all moving pistons in one caliper (four in my case), or do I only really have just two pistons? Also, what is the ideal braking ratio for modern sportbikes? What do you guys think? Did I do my math correctly? Thanks guys!

[TOOLS1]

Without knowing the diameter of 1 piston (assuming they are all the same diameter) I could not even begin to check your math.
TOOLS

[surfish95747]

Oh sorry duh. I one caliper I have both a  30mm and a 26.9mm pistons.

On Feb 28, 2016 2:33 PM, "TOOLS1 [via Honda CB750'S]" <[hidden email]> wrote:

Without knowing the diameter of 1 piston (assuming they are all the same diameter) I could not even begin to check your math.
TOOLS

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[surfish95747]

Okay I did a little more talking with VintageBrake.com and they mainly deal with vintage brakes as their name says. However he did tell me that for these modern sportbike brakes the ratio to shoot for is around 33:1. And even then, when going from vertical/horizontal to radial master cylinders that changes the geometry of the master cylinder throwing that ratio off. Where using the horizontal master cylinder you'd be looking for a 33:1 ratio, if the piston size that gives you is a 14mm piston, you'd want to go up around 3mm's in piston size for a radial master cylinder. So not an exact science but pretty cool to figure out what works best. Anyways, it was fun to look at and see what works best.