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question kevin. on a dual sided caliper, such as my 4-piston Brembos from Viper or your 8-piston Brembos from Merc, you ignore one side of pistons because of how they push against each other and cancels out some of that line pressure.



The pistons are the same size left and right. That means you have to divide the measurements by two. When you finish the equation you have to add the numbers together to get a total. You just did extra work and cancelled it out in the end.

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Does that mean your brake torque calculation where you double it for the other pad, should not be doubled? or do you still double that number because you already accounted for the "loss" of piston force from the opposing pistons?



The torque calculation solves for rotor force. The brakes grab both sides of the rotor with the same force due to that whole equal and opposite reaction thing. Since you have drag on both sides it adds together.

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And what about the coefficient of friction between the pad/rotor? should that be accounted for somewhere?
---or is that some of the details that you said an engineer would throw a fit over?




You are correct. The coefficient of friction divides the brake torque. In the sample above we had the magic brake pads with a coefficient of 1.
This is indeed where engineers begin frothing at the mouth. Brake fluid compresses. Different fluids compress at different rates as temperature changes and water content increases. Rubber brake hoses stretch. Steel brake lines stretch. All kinds of other things come into play.

If you want to get technical, everything I listed is "useless" to a Formula 1 team. Pedal pivot friction, play between the mechanical bits, minute amounts of air trapped in the lines, and all kinds of other stuff changes the numbers.

I was going to build an Excel spreadsheet that would allow people to enter their measurements and get the answers but I have nowhere to host it.

This was meant to be a quick and dirty way to run the calculations.
It sure is dirty but there was nothing quick about it.

Hopefully it will help a few people get a rough idea of what's going on in the brake system.

We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon