47-55.1 Brake line flaring sizing help

[b-mac]

So my oem s10 master cylinder has two different fitting sizes on the outputs. Maybe 7/16 for the front, and 3/8 for the rear.

I'm using an aftermarket adjustable proportioning block that uses all 3/16 fittings. I have 3/16 line.

My question is, can I bubble flare the 3/16 line, and use this (pic below) 3/8 fitting that seems correct, or will I have trouble with the bubble seating? Same question for the even larger 7/16, but I did find a brass adapter from 7/16 to 3/16 that should work.

[joedoh]

thats what I do, reuse the fitting. the s10 fittings are weird sizes, makes it a pain to buy adapters. I tried to put together a chart of fitting sizes and adapters, I will look for it but honestly just new line and the old fitting works.

[b-mac]

Cool. That's what I was looking for. It's been a while since I've done any flaring. Getting it right the first time would be great.

[sack54]

They make adapters for brake fittings, so you can make them all the same if you really want to.

[mr48chev]

As Sack54 said the right adapters are out there but my experience is that they aren't always easy to find.

I fought a leak on an OT mini van I had and finally jacked the line off another mini van that I use for storage to fix the problem. I made up several lines an never got it to where it was completely sealed. It didn't visibly leak fluid out but after a few days air would get in the line and I'd have to bleed the brakes again.

[b-mac]

Oh good, a Horror Story!

Just what I was looking for Mr.48 !!

[ndeep]

bubble flare ? like a vw ?

[mongocanfly]

If your making your own lines they make both thread size nuts for 3/16 line...

[b-mac]

Ndeep,

Technically it's a double-bubble.

Also, thought I'd share the big reveal.

[mr48chev]

OBTW single isn't legal for brakes with steel brake lines. For steel you have to have a double flare or the later metric bubble flare.

[joedoh]

looks poyfect!

[dsraven]

looks like you got it figured.
just as a side bar for others doing the same thing, check with local laws because some of the adapters are brass and not legal for brakes in some places. a lot of OEM lines have a coupler mid-line that is brass but some are also steel, dunno how they get away with some things but whatever, it works.hydraulic shops may also be able to help you out if you have the fitting sizes and need help with the flaring side of things. they also make flexible stainless lines with whatever fitting you need on each end. they look clean under the hood too. one thing I have done in the past when the connections are really close together is to use a line that is too long and then make a circular loop. it gives more room on the line for the flare tooling when working that part and also adds some maneuverability for connecting and screwing the parts together straight. just be sure to keep the line going downhill to one end so it will bleed easier and not trap a bubble. make the flares then wrap the line around a coffee can or something to get the loop. some of the newer vehicles also use a stainless flexible line from the master to the ABS unit. maybe one of those would have the correct fittings and you could be done in a single step or with a single adapter fitting.

[b-mac]

dsraven,

Interesting knowledge here. Especially about the Single vs. Double Flare and DOT regulations.
I learned that you can't "Double Bubble" or Invert Flare a Stainless Steel line, so I guess all of those SS conversions are possibly non-DOT compliant ?!

As are the Stainless Steel flexible lines that I used from this kit:

https://www.speedwaymotors.com/Mild-...e-Kit,999.html


"connections are really close together....then make a circular loop" - This point is why I went out and around and back between the maser and block, rather than just a quick turn-down.

Reading this forum, you will find those who have never put a loop in brake line (such as under my block) and never had any issue. I prefer just a bit of 'give' since the cab and frame are independent of one another.

[dsraven]

yup, thats why I mentioned it. best to know before spending money and then possibly not passing an inspection.
on some of the brass fittings I can actually see why they would be suspect for a brake system. hydraulic pressure in a brake system can spike at around the 2000 psi range (not gonna see that most likely but possible I guess, and some sites would say 4000 psi from engineering standpoint for caliper capabilities etc) so I can understand how a few threads into a brass fitting could strip out under pressure. personally I like to use the strongest and best stuff possible for my ride. it's my butt in the seat, why scrimp on the basics for the sake of a few bucks. I have often re-used a flare nut when fabbing brake lines if I can't find a new one in stock when under the gun to get something done. but if it is my project it has probably been in the shop for a long time anyway, lol. just order the right part and wait a couple days to get it. a couple of days isn't gonna make a big difference. if re-using an old fitting check for burrs or pitting on the edge that backs up the tubing flare, the hole for the tubing to pass through is actually still round and ensure the threads are in good shape.

[jmlloar]

Every time I did this Just take the master cyl with you to advance auto.

They have lines with master cyl size on one end and common size on the other. about 8 inch long pieces.

[b-mac]

Originally Posted by jmlloar

Every time I did this Just take the master cyl with you to advance auto.

They have lines with master cyl size on one end and common size on the other. about 8 inch long pieces.

I wish I had known this a week ago...

Although, if this is true, then it means that a 3/16ths inverted bubble flared line will "seat" into a larger bubble line female, even if said female fitting initially accepted a larger brake 'line'.

This is what I did on the rear line.

[jmlloar]

I have done this many times. they even have some in the metric fitting sizes.

They are just like the factory ones with big fitting with small hole and smaller line

[dsraven]

I was gonna suggest the same, take the parts with you for match up. master and prop valve.
bench bleed is recommended before putting master back on anyway so might as well remove and take with you. also gives opportunity to flush the reservoir so you have nice clean res before you put new fluid in and disturb old dirt that settled out in the res. a plastic pump sprayer works for that. use brake fluid to clean/flush. then bench bleed master and install. check pushrod clearances at pedal and from booster at same time.