Go Back   986 Forum - for Porsche Boxster & Cayman Owners > Porsche Boxster & Cayman Forums > Performance and Technical chat

Reply
 
LinkBack Thread Tools Display Modes
Old 03-17-2015, 11:08 AM   #1
Registered User
 
Join Date: Dec 2014
Location: SF Bay Area
Posts: 239
Hard brake lines

Hey guys, I have a question about the bubble flare on the hard brake lines. I read on some other forums that its a compression seal and once broken, it can not be reused because it won't seal. You have to cut the flare off and reflare the tube. Is this true?

Also, does anyone know the tread size on the flare nuts? There are two different sizes. I would like to get some new nuts.
martsink is offline   Reply With Quote
Old 03-17-2015, 12:29 PM   #2
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,102
Quote:
Originally Posted by martsink View Post
Hey guys, I have a question about the bubble flare on the hard brake lines. I read on some other forums that its a compression seal and once broken, it can not be reused because it won't seal. You have to cut the flare off and reflare the tube. Is this true?

Also, does anyone know the tread size on the flare nuts? There are two different sizes. I would like to get some new nuts.
Most brake hard lines are a double flare style, which requires specialized tooling to create. Because of the pressure they operate under, they cannot be made with a common single flare tool. Flare fittings can be opened repeatedly and will completely reseal as long as neither side of the flare fitting is damaged in anyway.

Fittings on Porsches are metric and tend to use 18MM, 17MM, 14MM and 11MM, depending upon year, model, and location of the fittings. There may also be one of two other odd sizes, again depending upon the car. You should never attempt using an open end wrench on a brake line fitting, you need proper flare fitting wrenches to have any chance of preventing rounding off the flats on the fittings:

__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
JFP in PA is offline   Reply With Quote
Old 03-17-2015, 03:48 PM   #3
Registered User
 
Join Date: Dec 2014
Location: SF Bay Area
Posts: 239
Quote:
Originally Posted by JFP in PA View Post
Most brake hard lines are a double flare style, which requires specialized tooling to create. Because of the pressure they operate under, they cannot be made with a common single flare tool. Flare fittings can be opened repeatedly and will completely reseal as long as neither side of the flare fitting is damaged in anyway.

Fittings on Porsches are metric and tend to use 18MM, 17MM, 14MM and 11MM, depending upon year, model, and location of the fittings. There may also be one of two other odd sizes, again depending upon the car. You should never attempt using an open end wrench on a brake line fitting, you need proper flare fitting wrenches to have any chance of preventing rounding off the flats on the fittings:

Thanks for the reply. I'm aware of the flare types and flare nut wrenches. The nuts were not rounded, I just to to replace them because I have a chance to. Part of the line on my car has quite a bit of rust on it, so I would like to replace it. I plan on either buying or renting a flare tool and a tube bender.

I actually found a video that explains the tube flares. It's confirmed that you can not reuse european style bubble flares (at 2:08). https://www.youtube.com/watch?v=_C12aUE6Qlk
martsink is offline   Reply With Quote
Old 03-17-2015, 05:16 PM   #4
Registered User
 
Join Date: Dec 2012
Location: DE
Posts: 123
If you are making your own hard lines, I suggest checking out copper/nickel tubing. Much easier to work with and doesn't rust.
example: JEGS NiCopp Nickel Copper Brake Lines - Free Shipping on All Orders @ JEGS

Last edited by spendy; 03-17-2015 at 05:29 PM.
spendy is offline   Reply With Quote
Old 03-17-2015, 05:25 PM   #5
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,102
Quote:
Originally Posted by martsink View Post
I actually found a video that explains the tube flares. It's confirmed that you can not reuse european style bubble flares (at 2:08). https://www.youtube.com/watch?v=_C12aUE6Qlk
You do not have "bubble style flares" on the car which are used on soft steel lines, the ones on the car are double flares in hard steel lines which remain fixed, and are completely reusable. We open up these double flares regularly, and have never had a problem with them resealing.

__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein

Last edited by JFP in PA; 03-17-2015 at 05:31 PM.
JFP in PA is offline   Reply With Quote
Old 03-17-2015, 05:29 PM   #6
Registered User
 
Join Date: Dec 2014
Location: SF Bay Area
Posts: 239
Quote:
Originally Posted by JFP in PA View Post
You do not have "bubble style flares" on the car which are used on soft steel lines, the ones on the car are double flares in hard steel lines which remain fixed, and are completely reusable. We open up these double flares regularly, and have never had a problem with them resealing.

Oh cool, good to know! Thanks!
martsink is offline   Reply With Quote
Old 03-19-2015, 09:21 AM   #7
Registered User
 
Join Date: Dec 2014
Location: SF Bay Area
Posts: 239
Quote:
Originally Posted by JFP in PA View Post
You do not have "bubble style flares" on the car which are used on soft steel lines, the ones on the car are double flares in hard steel lines which remain fixed, and are completely reusable. We open up these double flares regularly, and have never had a problem with them resealing.

Hey, I'm just at the shop looking at the brake lines and it looks a lot like the bubble design. Could you please have a look at the pics( I'm sorry about the size, I'm on my phone). What do you think?



The reason I decided to double check because I though that double flare is only used in american cars.
martsink is offline   Reply With Quote
Old 03-19-2015, 10:38 AM   #8
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,102
That is a DIN/ISO double flare (sometimes call a "mushroom" flare), which is reusable:

If the end of the tubing looks like a button and the back side angle of the flare is 90 degrees it is the DIN flare. If you look at the true "bubble" photo above, the back side is rounded. You must use a nut with a "lead" for the DIN flare (nut has unthreaded tip).



M1-3 10 x 1.00MM common European/DIN nut with DIN flare

To make this style flare, you need a very special style of tool.
__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein

Last edited by JFP in PA; 03-19-2015 at 11:10 AM.
JFP in PA is offline   Reply With Quote
Old 03-20-2015, 08:29 AM   #9
Registered User
 
Join Date: Dec 2014
Location: SF Bay Area
Posts: 239
Quote:
Originally Posted by JFP in PA View Post
That is a DIN/ISO double flare (sometimes call a "mushroom" flare), which is reusable:

If the end of the tubing looks like a button and the back side angle of the flare is 90 degrees it is the DIN flare. If you look at the true "bubble" photo above, the back side is rounded. You must use a nut with a "lead" for the DIN flare (nut has unthreaded tip).



M1-3 10 x 1.00MM common European/DIN nut with DIN flare

To make this style flare, you need a very special style of tool.
Hey,
I don't want to get into a technical argument because I'm no an expert myself, but DIN or ISO is a "bubble flare", I believe double is the term for SAE flare. I just spoke to my local Porsche mechanic about it, and he said they are technically not reusable because they have a crush zone for sealing, but 90% of the time you won't have any issues with it. He said when he does the work for customers he would have to re-flare the line, but he wouldn't worry about it on a personal car.
martsink is offline   Reply With Quote
Old 03-20-2015, 09:51 AM   #10
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,102
Quote:
Originally Posted by martsink View Post
Hey,
I don't want to get into a technical argument because I'm no an expert myself, but DIN or ISO is a "bubble flare", I believe double is the term for SAE flare. I just spoke to my local Porsche mechanic about it, and he said they are technically not reusable because they have a crush zone for sealing, but 90% of the time you won't have any issues with it. He said when he does the work for customers he would have to re-flare the line, but he wouldn't worry about it on a personal car.
Calling it a bubble flare is a common misnomer, I have even seen it listed in publications that way; and it is completely reusable.
__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
JFP in PA is offline   Reply With Quote
Old 03-20-2015, 10:15 AM   #11
Registered User
 
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 5,102
I've just searched some brake line manufacturer's websites, and you may have a point as some are listing their versions of it as a "DIN/ISO "bubble" style". All of the old bubble type fittings I am familiar with (found on Alfa, Fiat, etc.) the completely rounded bubble tube end either crushed or deformed the first time it was tightened, making it impossible to reuse, and was typically found only on soft alloy tubing. The DIN/ISO type has a 90 degree back angle rather than a curved surface, uses a special nut, does not deform unless seriously over tightened, is found only on hard steel (read difficult to shape or bend) tubing, and is used on many different manufacturers, including several US cars like the Corvettes.

As I mentioned previously, we put them back together all the time and have never had one leak.
__________________
Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein

Last edited by JFP in PA; 03-20-2015 at 10:34 AM.
JFP in PA is offline   Reply With Quote
Old 03-20-2015, 10:44 AM   #12
Registered User
 
Join Date: Jun 2014
Location: LB, Germany
Posts: 1,322
JFP in PA is right.

This brake lines are reusable as long as they are not damaged by an accident, by rust, or something else. If the line has corrosion, please allways replace it. Take care of the tip. This has to be 100% intact. Else please replace. If you not 100% shure, replace it. Brakes systems are essential for your and others lives. Don't make savings at the wrong spot.

Regards Markus

Last edited by Smallblock454; 03-20-2015 at 10:54 AM.
Smallblock454 is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -8. The time now is 09:00 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page