Thread: Brake line diameter??

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Hi everyone! I just joined about 5 min ago. So far I like what I see!!

My question is in regards to my 64 Chevelle. Does anyone know the correct diameter of brake line to use from the distribution block to the rear brake splitter? The car is four wheel drum at the moment but i'll be installing a factory front disc setup asap.

Thanks for the help!

anyone?

It may be 3/16, possibly 1/4. Your going to have to measure it. I heard some GM's used 1/4 to the back, 3/16 up front.

Thanks. I'm pretty sure mine is 1/4''. I was just wondering if one was better or gave better braking performance... Would both sizes give the same pressure???

Originally posted by Kevyd
Thanks. I'm pretty sure mine is 1/4''. I was just wondering if one was better or gave better braking performance... Would both sizes give the same pressure???

Pressure is equal and undimished in all and opposite directions.
Size indicates volume per application.

The pressure would be the same regardless of size, BUT, (I think this is how it works) the more volume you have, (ie- diameter) the more force you can apply.
Think of it like a uniform force per some unit area, applied to a piston for instance. If you have the same pressure (force/area), and two different areas (one piston bigger than other) you will have more force on the bigger one (pressure X's area).

A bigger brake line carries the same pressure, but you have the ability to apply it to more area. Since you are splitting it in the rear, you want to start out with more so that you are left with an adequate amount once you split.

My truck has the same deal, I have a 1/4" going to the rear splitter, and 3/16" going out to each rear wheel. The front uses two independant 3/16" lines.

I may be wrong about my theory though, I'm not a hydraulics expert. It seems to make sense though.

Thanks! That makes good sense...

if you need more help try www.teamchevelle.com

The pressure would be the same regardless of size, BUT, (I think this is how it works) the more volume you have, (ie- diameter) the more force you can apply.
Think of it like a uniform force per some unit area, applied to a piston for instance. If you have the same pressure (force/area), and two different areas (one piston bigger than other) you will have more force on the bigger one (pressure X's area).

A bigger brake line carries the same pressure, but you have the ability to apply it to more area.

While most of what you say seems logical, it's not correct when related to line size. 100 PSI at a 4 sq. in. caliper is going to provide 400 lbs of force (100 lbs/sq in x 4 sq in), whether it comes through a 1/8" line or a 2" line. The real advantage with a larger line is slightly reduced line loss due to restriction in the line, and a better pedal feel. For example, it you put a 1/64" orifice in the brake line, you would have terrible pedal feel because you'd have to overcome the resistance of pushing all that fluid through that tiny hole. Eventually, the pressure would come up to to 400 lbs, but it would take way too long, hence the bad pedal feel.

Your explanation does apply when you're talking about changing the piston size. A larger piston in the caliper would result in a proportionately higher pressure (proportional to the area, that is.)

Originally Posted by Henry Rifle

While most of what you say seems logical, it's not correct when related to line size. 100 PSI at a 4 sq. in. caliper is going to provide 400 lbs of force (100 lbs/sq in x 4 sq in), whether it comes through a 1/8" line or a 2" line. The real advantage with a larger line is slightly reduced line loss due to restriction in the line, and a better pedal feel. For example, it you put a 1/64" orifice in the brake line, you would have terrible pedal feel because you'd have to overcome the resistance of pushing all that fluid through that tiny hole. Eventually, the pressure would come up to to 400 lbs, but it would take way too long, hence the bad pedal feel.

Your explanation does apply when you're talking about changing the piston size. A larger piston in the caliper would result in a proportionately higher pressure (proportional to the area, that is.)

And a proportionatly longer pedal throw.

And a proportionatly longer pedal throw.

Yep. Pascal was pretty much on the mark.