My hydraulic rendition of braking.
MC bore and stroke determines displacement. The amount of fluid the MC pushes out on a pedal stroke should match the displacement required to force each caliper piston out of its bore, creating the clamping force of the pad against the rotor prior to the pedal reaching full stroke. I shoot for 1/4 stroke leaving pedal travel to create pressure required to clap the pad against the rotor.
Pedal ratio, caliper piston displacement and MC displacement all affect the amount of fluid delivered to the caliper and the foot force to deliver such. We all have varying level of strength and desire in our left legs to accommodate such work and we all have various room for pedal length. All variables
Brake fluid is not compressible. The amount of fluid put into the brake line via the mc equals the amount of fluid that leaves the line into the caliper. The line will gobble up pressure in friction loss as it moves through the line.
The desired result of the braking system is to build pressure at the caliper to force as much fluid as needed into the caliper to stop the vehicle. If the energy is being spent to get the fluid through the smaller line there is less energy available to move the caliper pistons.
Line size is a compromise of physics, amount of space and economics. The remaining factor is that braided line will swell to some degree during under pressure. This increase in line diameter will rob volume needed at the caliper and become wasted energy in the system, causing an increase in input energy for no gain in stopping power. Nylon lines are even worse IMO.
Now introduce hydroboost into the equation, or any type booster for that matter. Wilwood MCs create approx 1000psi of pressure when the displacements are correct. Hydroboost can create as much as 2500psi of pressure.
This increase in pressure does a couple things for us. It helps overcome the friction losses in the line as well as decreasing the amount of energy put on the pedal by supplementing it with an alternate energy source. The net effects of losses are less prevalent because of the reduced effort applied at the pedal.
-4 lines are certainly not the fix all but in my mind and per what I know about fluid movement, hydraulic engineering and application as well as energy efficiency a larger line size can not hurt a thing post bleeding process.
The cons to a larger line...cost, room, more difficult to bleed and increased risk of line swell.
I was successful in having great manual brakes with Wilwood 4 piston dynalites, a 3/4" MC for each axle and -4 line. After 3 left knee surgeries my leg looks like a science fair project and is weak. I simply can't apply an abundance of pressure to the pedal which is why I use hydroboost on everything. I went with manual brakes on my Jimmy's car because that's what all the cool kids do. I fell victim to the same follow the pack that brake line size is grouped into. They were good but they were no hydroboost setup! I won't ever go back especially since someone took the time to design a nice clean and small unit that works great in a buggy.
Check this out, I have it in my new buggy and it flat works awesome. Minimal effort and it drives a small and cheap OEM 4 piston caliper that can also be provided.
http://www.wideopendesign.com/Product/10872/Hydroboost-Brake-Assembly.aspx
Here is a picture of it in my buggy
The caliper on the WOD scalloped rotor
The brake pads can be changed without removing the caliper from the buggy.
I'm no brake system expert but I do have a fair amount of hydraulic and fluid energy knowledge. This is what I know and how I translate it to stoping a buggy. I've been pretty successful at having good brakes on every rig I've owned whether it be manual, vacuum boosted or hydroboost.
