Thread: Brake help
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Old 04-04-2003, 11:28 AM
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rdorman rdorman is offline
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Join Date: Aug 2001
Location: columbus, Oh
Cobra Make, Engine: Unique 427 roadster with 351C-4B
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Default Brake help

As some of you know I have been 're-engineering' the brakes on my car for some time. I recently purchased a copy of Fred Puhns Brake Handbook. This book has it all. With the formulas in the book you can engineer a complete braking system from scratch.

I used it to take my existing components and determine different master cylinder sizes, balance and pedal effort for maximum braking. I have yet to put the cylinders on the car but it falls right in line with the expert recommendation I have been given. If you ever need to work through brake changes or issues, you must get your hands on a copy.

If there is enough interest, I will take the time to post the formulas. There are some tough items that you will need to know. Some you can get from the various manufacturers, some you will have to make a best guess at. If you are just looking to determine the correct master cylinder sizes, you will need to know items like:

- tire grip and diameters
- calipers piston size, number of pistons and fixed or sliding mount
- rotor diameter
- pad width and coeficient of friction
- center of gravity both height and fore and aft
- aerodynamic lift and downforce (even though we all know the cobra body lifts I went with a force of zero. When lift is present, the brake will lock easier than when lift is not present.)
- pedal ratio and type (bias bar, non-bias bar, dual master or single)

Off the top of my head that is most of the data required. CG height is a tough one. There are way to estimate it though. I used a commonly thrown about heigth of 17" for Cobras.

Book even shows how to calculate temp rise from kenetic energy. Way cool


What a hobby

Rick
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