P15 Brake Pedal Ratio

[Drdialtone]

OK, after culling through many, many, many previous posts concerning brakes and brake upgrades and brake conversions and master cylinder upgrades, I still can't find what I am told is a very important data point; brake pedal ratio.

Found lots of information and recommendations on which m/c to buy, locations for the disk conversion kits, etc., but not the ratio. Is this a standard measurement? Is this in a shop manual? Thanks!

[oldodge41]

http://www.ecihotrodbrakes.com/images/pic01_brakefacts.gif This is the simplest explanation I have found.

[james curl]

The only pedal I have loose is a 41 Dodge brake pedal. It mounts on the master cylinder which is the same master cylinder used on the P-15 cars. The measurements are, from the center of the brake pad to the center of the trunnion pin is 11.5" and from the center of the trunnion to the center of the push rod hole is 1.5625" for an effective ratio of 7.54:1. A pedal ratio of 5:1 to 6.5:1 is acceptable for manual brakes. The larger the ratio the softer the pressure to activate the brakes will be, assuming a 100 pound force on the pedal at the pad using a 7.54:1 ratio results in a 754 pound pressure on the master cylinder, a 5:1 ratio would result in a 500 pound pressure for the same 100 pounds of pedal pressure. Now that you are thoroughly confused, thats the best I can do to answer your question.

Edited July 13, 2011 by james curl
addition information

[Drdialtone]

The only pedal I have loose is a 41 Dodge brake pedal. It mounts on the master cylinder which is the same master cylinder used on the P-15 cars. The measurements are, from the center of the brake pad to the center of the trunnion pin is 11.5" and from the center of the trunnion to the center of the push rod hole is 1.5625" for an effective ratio of 7.54:1. A pedal ratio of 5:1 to 6.5:1 is acceptable for manual brakes. The larger the ratio the softer the pressure to activate the brakes will be, assuming a 100 pound force on the pedal at the pad using a 7.54:1 ratio results in a 754 pound pressure on the master cylinder, a 5:1 ratio would result in a 500 pound pressure for the same 100 pounds of pedal pressure. Now that you are thoroughly confused, thats the best I can do to answer your question.

James - you are my personal hero!!!! Thanks!