Anyone have big brake lines?

[Swar]

My '71 has the original manual master cylinder with proportioning valve and a big brake line going to the rear, splitting into 2 normal size lines. Fronts are also normal size. Anyone have the same setup or know why the rear line is bigger?

[kwmech]

1/4'' line to the rear is normal in the earlier years on these GM trucks.

[davepl]

In theory the rear line has to carry enough fluid volume for two cylinders whereas on the front each has a dedicated line from the combo valve, so it stands to reason that it'd be larger.

In theory, line size doesn't matter for hydraulics except for speed of response. You could have the line go into a (very rigid and well sealed) 50 gallon drum in the trunk and back out and it'd still work... in theory.

[Swar]

Got it. Thanks for the input. I'm usually one to say if it ain't broke, don't fix it... but I broke it. I'll just replace the section with the same size.