DIY Brake Line Q's

themilkguy · Post by **themilkguy** » Sat Jul 21, 2012 5:47 pm

Hey folks,

Figure some new steel lines up front are in order. I bought some 3/16" lines from a local shop, but when I got it home and did a side-by-side comparison the inside diameter seems larger than the old. Anyone think my eyes deceive me?

Also, considering the cost savings I think I'll just buy a roll of metric line and make my own lines. Can anyone confirm what I already think - that we need a bubble-flare end on the line?

Thanks in advance,
C

Mike W. · Post by **Mike W.** » Sat Jul 21, 2012 6:59 pm

Yes on needing the double or bubble flare, if anything has to be right it's brakes. But check out Realeom, they look cheap new. They come straight so you have to bend them, but you'd be looking at that anyway.

http://realoem.com/bmw/showparts.do?mod ... g=34&fg=15

themilkguy · Post by **themilkguy** » Tue Jul 24, 2012 4:52 pm

Thanks Mike - a 25' roll of 3/16" was only $12, so since I already had the bubble flare tool and pipe bender I thought it would be in my best interest to be ready to replace as much of the 40 year-old brake line as necessary.

Could you confirm the proper fitting for me? It's called an "M12", right? And does the fitting have to specify "bubble" as well?

Cheers

Mike W. · Post by **Mike W.** » Tue Jul 24, 2012 9:13 pm

themilkguy wrote:Thanks Mike - a 25' roll of 3/16" was only $12, so since I already had the bubble flare tool and pipe bender I thought it would be in my best interest to be ready to replace as much of the 40 year-old brake line as necessary.

Could you confirm the proper fitting for me? It's called an "M12", right? And does the fitting have to specify "bubble" as well?

Cheers

I can't confirm because I don't know on the sizes. I've heard the flare referred to as both a "bubble" and a "double", I think the latter is what the Germans call it. I've only done single flare as on refrigeration and water so I'm a little weak here. Actually thinking about it, M12 sounds too large, it's an 11MM nut and I don't think the threads are larger than the flats of the nut, though I don't have one at hand to look at.

Blaise · Post by **Blaise** » Wed Jul 25, 2012 11:50 am

It is a bubble flare, which as I understand, is a form of a double flare.

It is important to understand the difference. If you look at the ends the BMW uses, you will understand right away.

A single flare, simply flares the end of the line in a conical shape.

A typical double flare is the same as above, but the line is folded back onto itself, creating a double thick lip. The result is still a conical shape (inverted).

Lastly, the bubble flare has the line material doubled up, but leaves the cone shape opposite.

I found this on the web....ignore the dates. Bubble flare on the right, standard double flare on the left.

2 and 3 are bubble flares

Lastly, I found a few tricks to doing them right....so ask if you run into trouble.