Brake lines: double flare or bubble flare?

[drWmN]

Hi all!

 

I need to replace a brake line in my 2002 '73 Automatic because it's leaking.

Should I do a double flare or a bubble flare on the copper lines?

 

I've watched a LOT of videos and found a LOT of forum posts about this, but all of them are saying something different...

 

It seems like a single flare is just out of the question for brake lines, but is there a big difference between a double flare and a bubble flare?

 

Any input will be much appreciated.

Also: if there's already a post for this, I'm sorry for double posting. I couldn't find an existing thread for this.

[tzei]

DIN/ISO bubble flare.

[AceAndrew]

Bubble flare.

 

and no straight copper.  If using Cunifer/NiCopp, beware of Chinese line (lots of rebranded stuff littering Amazon).  Burst test results are all over the place. This is a part where you’ll want to use a quality USA made line.

[NYNick]

I used FedHill in Oxford, Mass for my Cunifer. Doubt they'll sell you only one small brake line though. I did the entire car.

[TobyB]

Bubble flare is  very different from double flare.  You want bubble flare.

It IS possible to make one's own, but personally, I don't trust mine.

And certainly not in a country that takes safety seriously.

("The United States- where Safety is primarily a legal concern.")

 

In this country, bubble flare lines are available pre- made in approximately 3" increments-

which works for everything except maybe the steel lines on the front struts.

 

t

[tzei]

Depending of tooling you have with Ni/Cu pipe you may want to start forming as single flare and about after 1-2 mm you’ll change for bubble flare tooling. Ni/Cu is harder than plain Cu so it’s easier to form bubble big enough this way. Takes practise so try it out fist couple of times. Plain Cu pipe bubble forms at one go. To check (finsh)the bubble i tighten newly made fitting to a female fitting. Compare to factory bubble that you have enough sealing area.

 

Cheap tools = poor quality

 

 

Edited August 16, 2023 by tzei

[wheelieking]

I replumbed the entire brake system on my '76 with Cunifer from Fedhill and Bubble flare.  I used the existing brake line as a template and bent the new line to match as close as possible. Worked great. 

 

Just make sure to take a small section of tubing you don't care about, and flare both ends of it before you put the fitting on it, just to get that mistake out of the way. 😉  LOL 

 

Fedhill brake line - Where to buy brake line, fuel line, brake line flaring tools, brake line nuts and brake line fittings

WWW.FEDHILLUSA.COM

 

[cda951]

The expensive, high-quality flaring tools are best (see pic below of the nice vice-mounted Stahlwille one we use at my shop), but with good prep of the line, the cheap ones can still do a decent flare in a pinch. Those of you who followed my recent Alaska road trip adventure in out 2002tii might recall that the only issue we had was a fatigue crack of a brake line at the base of the flare near the border of Alaska and Yukon . . . . and I did not pack any of my flaring tools!

 

Luckily I did pack a lot of other tools including the small files that I normally carry in our rally toolbox, in addition to a mini tubing cutter----we found a fellow Lemons Rallyist to bring us a cheap NAPA flaring kit, which did not include the tubing cutter. The key is to very gradually cut the line with the tubing cutter, don't use too much pressure or the line might be crushed. One the cut is made, a few minutes of de-burring the OD and ID of the brake line and lightly filing the surface flat will ensure a decent flare, even with a cheap tool.

 

The "first step" of a cheap universal double-flaring kit is a facsimile of a DIN bubble flare and will work in a pinch, even on a 50+ year old steel line. While stuck at the service station in Beaver Creek, Yukon, I got a good bubble flare on the first try after prepping the line as described above (careful setting of the split dies also helps), and it did the job for the 4,000+ mile journey home. 

 

If you are able to take your time at home, invest in a good tool or at least borrow one, and practice with some old lines.

 

And yes, remember to install the fitting on the line before flaring

 

 

 

[Son of Marty]

6 minutes ago, cda951 said:

And yes, remember to install the fitting on the line before flaring

Yeah, and make sure the fitting facing the right way. 

[Tdh]

If you’re dead set on making the lines yourself spend the money on a Mastercool flaring tool if you can afford it. It’s the best I’ve ever owned hands down. Expensive but worth it. 

[Dudeland]

I am a big safety type of person, and perhaps have a bit of a reputation online for being vocal about these things. 

I have lived long enough to see other people deeply (deeply (deeply)) regret cutting corners on safety.  I could go out and get the best brake line tool that you can think of, and still, there is no way in all of god's creation that I would futz around with brake lines. 

 

Get less chrome,  use those older seats, ignore the smelly and ripped carpet... put off a re-spray, use powdered milk( and I love milk)  and get something like these. 

 

 

Cunifer Brake Hardline Kit – 2002/Tii – Ireland Engineering | Racing & Performance Parts for BMW & MINI

WWW.IEMOTORSPORT.COM

---

Each Kit

 

BluntTech Industries • BMW 2002 Prebent SS Brake Lines

WWW.BLUNTTECH.COM

---

Prebent stainless steel brake lines for your standard 2002. Will also fit late 68's with 4 piston calipers

 

 

[scanner]

Brake Pipe Flaring Tool Professional In-situ 4.75mm DIN Hand Held FL27 - AB Tools Online

ABTOOLSONLINE.COM

---

AB Tools specialises in high quality tools suitable for professionals, enthusiasts and the keen DIYer! We pride ourselves on providing excellent customer service with our 100% satisfaction guarantee, ABToolsonline, ABTools, AB, Tools, Tool, Bergen...

Playing devils advocate I bought this tool a couple of years ago when I did the twin servo delete on my RHD car. I used cunifer lines and it did a good job, there were no leaks initially and after 2 years still fine.

[Lucky 7]

Bubble flare. I redid my whole system with NiCopp and a Harbor Freight tool. 

 

For those that might accuse me of being casual about safety, I had my stock lines explode while screaming down Lookout Mountain and narrowly avoided flying off a cliff like Toonces the driving cat.  Needless to say, I was motivated to get my brake system up to maximum safety. 😂

 

Just clean up your cuts and grease the flare tool at the head of the flare and it’s not difficult to get a good flare. 

[wheelieking]

On 8/18/2023 at 4:19 PM, Dudeland said:

......get something like these. 

 

 

Cunifer Brake Hardline Kit – 2002/Tii – Ireland Engineering | Racing & Performance Parts for BMW & MINI

WWW.IEMOTORSPORT.COM

---

Each Kit

 

BluntTech Industries • BMW 2002 Prebent SS Brake Lines

WWW.BLUNTTECH.COM

---

Prebent stainless steel brake lines for your standard 2002. Will also fit late 68's with 4 piston calipers

 

 

That is a great point.  I had forgotten I bought the IE set, but with the full Wilwood rear disk upgrade, I bent the hard lines for the trailing arms, and I had to bend the long single line that goes front to back to the triple junction in the drive shaft tunnel. 

 

Definitely buy pre-bent if you can though! 

 

 

[markmac]

FYI, if you are going to give it a go yourself, Bel Metric sells OE 'Cohline' fittings as well as epoxy coated steel lines.  They also sell copper/nickel in a roll.  I had no choice to make my own for the race car, I used the jenky old lines as templates.  Some super tricky bends, and I effed up more than once.  I used the steel / epoxy coated Cohline material.  One thing as well, IF the line goes through a grommet in the bodywork, get the grommet on before the fitting and the flare.  I used a Schwaben flaring tool, and I think my lines are all good - the proof will be in the puddin' when they get tested.  I don't see this as a 'safety' thing really.  You replace the lines, and you test them.  If they leak you either make another or you buy a pre-made new one and then test again.  Either they hold or they don't, doesn't seem to me like there is much middle ground on that (or am I missing something).  Hmnnnnn