I want to put together some good brake system numbers. Possibly when this is complete can re-post to the knowledge base.
For now I am just going to focus on the factory GM g-body vacuum brake system.
I have converted my car to the blazer front brakes, and S-10 rear wheel cylinders. I want to put the numbers together for the OEM setup as a baseline, and then compare to the blazer brake and S-10 wheel cylinders. I didn't notice a pedal feel difference going to s-10 wheel cylinders but after the blazer brakes I now have more pedal effort. The exercise is to calculate the different in pedal effort and travel before and after, with the moving the system closer to the feel of the original.
Here is the equations I have put together so far.
Line pressure (psi) = Leg Force (LB) X Pedal Ratio / MC Area (in^2)
MC volume displaced (in^3) = MC stoke (in) X MC area (in^2)
Force at Caliper (lb) = line pressure (psi) X caliper piston area (in^2)
MC stroke (in) = caliper stroke (in) * caliper area (in^2) / MC area (in^2)
I am not concerned with the amount of force added by the vacuum booster because it is a constant/unchanged between both system.
Average leg pressure applied to pedal is between 100-150 lb. I will use 100 in the equations
Pedal ratio is a constant between the systems, but I will enter the actual value.
I searched for over an hour on tb.com and could not find where anyone has posted the pedal ratio of the factory vacuum brake pedal. Does anyone know if not I will try to measure mine this week.
G-bodyMC bore is 15/16" - Someone please confirm and it is a single bore 15/16" for both halfs or is the MC dual bore?
Stock calipers piston 2 1/2"
Blazer calipers 46mm piston X2
This is only a 4% increase in area so that equals a 4% increase in pressure on the caliper to the pad.
g-body rear wheel cylinder 3/4"
S-10 rear wheel cylinder 7/8"
I will start searching and filling in the values as I find them.
G-body vacuum disk brake system front:
Line pressure (psi) = 100 (LB) X Pedal Ratio / 0.6899 (in^2)
MC volume displaced (in^3) = MC stoke (in) X 0.6899 (in^2)
Force at Caliper (lb) = line pressure (psi) X 4.906 (in^2)
MC stroke (in) = caliper stroke (in) * 9.812 (in^2) / 0.6899 (in^2)
Blazer disk brake conversion front:
Line pressure (psi) = 100 (LB) X Pedal Ratio / MC Area (in^2)
MC volume displaced (in^3) = MC stoke (in) X MC area (in^2)
Force at Caliper (lb) = line pressure (psi) X 5.14 (in^2)
MC stroke (in) = caliper stroke (in) * 10.28 (in^2) / 0.6899 (in^2)
G-body vacuum drum brake system rear:
Line pressure (psi) = 100 (LB) X Pedal Ratio / MC Area (in^2)
MC volume displaced (in^3) = MC stoke (in) X MC area (in^2)
Force at drum (lb) = line pressure (psi) X .8224 (in^2)
MC stroke (in) = caliper stroke (in) * caliper area (in^2) / MC area (in^2)
S-10 wheel cylinder conversion rear:
Line pressure (psi) = 100 (LB) X Pedal Ratio / MC Area (in^2)
MC volume displaced (in^3) = MC stoke (in) X MC area (in^2)
Force at drum (lb) = line pressure (psi) X 1.202 (in^2)
MC stroke (in) = caliper stroke (in) * caliper area (in^2) / MC area (in^2)