Brake Line

[rwolf]

I have converted my 59 GMC over to four wheel disc with dual master power brakes and proportion valve and the rear brake line kit came in and it is all 4an (7/16) but the rest of truck I have put 3an and 3/16 lines will running the two different size lines matter.

[Fred T]

I would prefer 1/4" tube. But 3/16 was used in some factory jobs with discs, so it should work.

[dwcsr]

-4 AN is 1/4" not 7/16". each -1 is a 1/16".
Disc brakes should be 3/16" line.
Drum brakes use 1/4".

[rwolf]

Yes you are correct 4an is 1/4 that was my slip up.

Thanks for noting that.

Will it matter on braking balance with having 1/4 line on the rear disc and 3/16 on the front disc?

Robert

[OrrieG]

Originally Posted by rwolf

Yes you are correct 4an is 1/4 that was my slip up.

Thanks for noting that.

Will it matter on braking balance with having 1/4 line on the rear disc and 3/16 on the front disc?

Robert

As long as your master cylinder has the capacity to move the larger amount of fluid the larger size will not be a problem. They are designed as a system with the MS sized to the line and caliper piston volume. Pressure stays the same regardless of line size but you need more volume in large diameter line. Drum wheel cylinder requires more volume than a disc caliper, hence large diameter line.

[dwcsr]

My understanding is that disc uses 3/16 front or back. Drum uses 1/4". It may throw off the balance. I used 3/16 on mine