1/4 to 3/16 brake line?

[Ishmael]

I'm finally getting back around to working on my Firebird. I hope I can get my brakes done this week and basically, I need to mount the booster and master and connect them to the ssbc propblock then bleed the brakes. You would think that would be easy. From what I remember the old gm master should use 1/4 line. The ssbc calls for 3/16 line. Can I go down to 3/16 line between the prop block and booster?
thanks
Scott

[MrQuick]

I usually keep those two as stock but I don't see why not. You don't need it now.

[Ishmael]

I would keep them stock but the fittings ssbc uses are just too tiny. I can see that the difference in the amount of volume isn't huge but I just wanted to make sure there won't be an effect.

[Apogee]

You can run everything with 3/16", so those two master cylinder lines at one size or the other should have no noticeable impact on your system. The smaller the tube diameter, the more rigid the line in terms of expansion due to pressure, so it's actually preferable in many ways. The OEM's are trying to keep their fluid velocities in check so as to avoid cavitation, the spontaneous creation of air bubbles due to turbulent flow, typically caused by excessive velocities through less than ideal fittings, ports, etc.

Tobin
KORE3

[Ishmael]

You can run everything with 3/16", so those two master cylinder lines at one size or the other should have no noticeable impact on your system. The smaller the tube diameter, the more rigid the line in terms of expansion due to pressure, so it's actually preferable in many ways. The OEM's are trying to keep their fluid velocities in check so as to avoid cavitation, the spontaneous creation of air bubbles due to turbulent flow, typically caused by excessive velocities through less than ideal fittings, ports, etc.

Tobin
KORE3

But if the rear was 1/4 and the front was 3/16 I believe that is what stock is) will the flares all connect inside the master? I know that you've said that about the size of the rest of the lines before. I know you've probably even said that to me. I just wasn't sure that would apply to those lines as well. So there should be no problem in the connecting inside the master?

[Apogee]

You typically have two outlet ports on the master cylinder, the size and configuration of those outlet ports is determined by the master cylinder you're using which you have not specified. Brake fittings however are quite often specified by their tubing diameter only, which is a terrible convention IMHO since it doesn't specify the thread designation and results in a confusing non-specific way of identifying fittings, however most sizes of tube nuts are available for several different tubing sizes. The smallest nut that you can use with 3/16" tubing is 3/8-24 SAE inverted flare. The smallest nut that you can use with 1/4" tubing is 7/16-24 SAE inverted flare. You can however also get 7/16-24, 1/2-20 and 9/16-18 inverted flare tube nuts for 3/16" tubing just as you can get 1/2-20 and 9/16-18 tube nuts for the 1/4" tubing, so matching your master cylinder shouldn't be that difficult.

The most important thing to get from this is that you need to make sure the tube nuts you use match both the fitting or port that you're tying into (both thread and type of flare) as well as the line size that you're using.

HTH,
Tobin
KORE3

[Ishmael]

And this is where I am confused. I bought the booster/master combo off the net. Actually Tobin, you told me what size bore to get based on my c5/c4 disc brake swap. Thanks for all the info over the last few years by the way. I went out (like an idiot) and bought the combo without asking what vehicle the master was specific to. I want to say it was from cpp. Its a gm master - I want to say "corvette style" as that's how I see them advertised. Its 9/16 on the back and 1/2 on the front. Problem is that I have two sets of lines. One is 3/16 and one is 1/4. I put all my brake parts in one box (like an idiot) and now I don't know which came with the master and since both sets of lines have the same size nuts I don't know which to use. Once I figure out which to use I'll either use an adapter (1/4 line) or flare on the new nuts from cpp (3/16 line). Now that we've established I'm an idiot for mixing all the parts up, is there a way to tell which line size it is supposed to be from looking at the ports in master?
The holes in both sides are the same size and a 7/64 drill bit will fit in the holes but not a 1/8.
thanks
Scott

[Apogee]

I'm finally getting back around to working on my Firebird. I hope I can get my brakes done this week and basically, I need to mount the booster and master and connect them to the ssbc propblock then bleed the brakes. You would think that would be easy. From what I remember the old gm master should use 1/4 line. The ssbc calls for 3/16 line. Can I go down to 3/16 line between the prop block and booster?
thanks
Scott

Okay, back to your original post, because I must not be understanding what you're asking. Correct me if I'm wrong, but you're just looking to connect the master cylinder to the SSBC distribution block, right? I assume the SSBC block has 3/8-24 SAE inverted flare fittings on all inlet and outlet ports, just like the other aftermarket options, so that will mean you need to connect using 3/16" hard lines since you cannot get 3/8-24 tube nuts for 1/4" tubing or run adapter fittings.

So, if you have 3/16" hard lines to connect from your master cylinder to your SSBC distribution block, use those. If you don't have them, make them and just recreate them like the 1/4" lines you have. Or, if you want to use 1/4" hard lines, then you'll need to run adapter fittings at the SSBC distribution block, something like a 3/8-24 male inverted flare X 7/16-24 female inverted flare. The master cylinder doesn't care whether you use 3/16 or 1/4 inch lines...makes no difference one way or the other.

Am I missing something?

[Ishmael]

[QUOTE=Apogee;880434]Okay, back to your original post, because I must not be understanding what you're asking. Correct me if I'm wrong, but you're just looking to connect the master cylinder to the SSBC distribution block, right?

You are Correct.

I assume the SSBC block has 3/8-24 SAE inverted flare fittings on all inlet and outlet ports,

Again, Correct

just like the other aftermarket options, so that will mean you need to connect using 3/16" hard lines since you cannot get 3/8-24 tube nuts for 1/4" tubing or run adapter fittings.

Still Correct

So, if you have 3/16" hard lines to connect from your master cylinder to your SSBC distribution block, use those. If you don't have them, make them and just recreate them like the 1/4" lines you have. Or, if you want to use 1/4" hard lines, then you'll need to run adapter fittings at the SSBC distribution block, something like a 3/8-24 male inverted flare X 7/16-24 female inverted flare. The master cylinder doesn't care whether you use 3/16 or 1/4 inch lines...makes no difference one way or the other.

Okay. As long as it will seal up at the master regardless of tine size I'm good. I was told that if it was 1/4 to start then I would have to use 1/4 now. Thanks for the help.