Why the larger brake line?

[Ford Freak]

A while back I purchased & installed a dual reservoir master cylinder w/proportioning valve kit for a 65-73 Mustang on my '56 Fairlane. This unit is for both power, or non-power brakes. The line from the master to the valve for the rear drum brakes is larger than the one from the master to the valve for the front disc brakes. I have noticed this on other kits available, as well. What is the reasoning for this? Thanks, F F

 

[Gene F]

Volume, and total force. It takes a little more to get the rears to work those wheel cylinders. For one thing, a wheel cylinder has two cups to actuate. Discs typically are one. There is a lot more to it than this, from an engineering perspective, but this is the short explination.

 

[Ford Freak]

A retired Ford mechanic once told me that the smaller the line, the more pressure. (or force?) Kinda like squeezing a garden hose. He said the larger line flows more volume. I never understood what that meant.???

 

[Gene F]

When it comes to brakes there is a ton of engineering involved. Surface area of the friction material, pedal ratio, proportioning valves, all kinds of stuff. The bore of the the master cylinder makes a big difference in pedal action.