Thread: To double flare or not????

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You know, I never really understood the reason for double flaring tubing. I presently have an all SS brake system on my roadster with all AN fittings that I installed myself and it the system works flawlessly with no leaks. I have spent 40 plus years in aircraft maintenance field and have never seen a double flare on an airplane where hydraulic system pressures reach 3000 PSI. To me, double flaring would seem to work harden the area of the flare. I have really never heard of a good explanation for double flaring, I'm sure there must be a good one, just never heard it.

Don't know if this is the answer your looking for but if you have ever flared steel brake lines with out double flaring they split. Why ????? All I know is when I started working on cars back with Fred and Barny I was told double flare so I do and I don't get leaks. I have done repairs on brake systems where someone used copper tubing inplace of steel with compresion fittings. There is probably a writen rule somewhere but I don't have a copy of it either.

You don't double flare in the aircraft industry because they use AN fittings only.
AN flares are 37 degrees and usually involve a tube sleeve to reinforce the tube.
Automotive stuff uses the double flare method because it's the most cost effective.they also use a 45 degree flare wich really thins and weakens the tube at the flare, hence the double flare. Why do they use the 45 degree flare ???? I would bet it had something to do with the tooling that was available way back when...

Originally Posted by cffisher

Don't know if this is the answer your looking for but if you have ever flared steel brake lines with out double flaring they split. Why ????? All I know is when I started working on cars back with Fred and Barny I was told double flare so I do and I don't get leaks. I have done repairs on brake systems where someone used copper tubing inplace of steel with compresion fittings. There is probably a writen rule somewhere but I don't have a copy of it either.

copper tubing used as brake line is illegal, and if it's found used in such a way on your car during a safty inspection by the police, the police can condem it right there on the spot, and you have to remove the vehicle from the street, and find another way home, not to mention fix it and then have a registered inspection station sign off on it, so they can clear the fix it tickit.

Originally Posted by Matt167

copper tubing used as brake line is illegal, and if it's found used in such a way on your car during a safty inspection by the police, the police can condem it right there on the spot, and you have to remove the vehicle from the street, and find another way home, not to mention fix it and then have a registered inspection station sign off on it, so they can clear the fix it tickit.

I would never consider using copper for a brake like, but I am also quite glad I don't live in New York....Never had a cop do a safety inspection on my car, and we don't have no stinkin' stickers!!!!!

Originally Posted by Dave Severson

I would never consider using copper for a brake like, but I am also quite glad I don't live in New York....Never had a cop do a safety inspection on my car, and we don't have no stinkin' stickers!!!!!

they will do a safty inspection on a car, right on the road side ( lights, any visible damage that is not legal, make shure the brake system and fuel lines are ok, but just a quick once over ) if there is probable cause that the car has saftey issues, and they'v arleady pulled them over. I think the safty inspection stickers are the best thing we'v got, yea, it cost's $20 per year for the inspection, but you know each and every car is safe ( now the entire inspection sticker is computerized, and goes right to Albany, no more inspecting another car, and using it's sticker ). the '96 and up stuff gets scanned too but, it's not too bad. Shops arn't going to pass a car with questionable workmanship, because if it's bad, it will come back on there liscense.

Originally Posted by Matt167

they will do a safty inspection on a car, right on the road side ( lights, any visible damage that is not legal, make shure the brake system and fuel lines are ok, but just a quick once over ) if there is probable cause that the car has saftey issues, and they'v arleady pulled them over. I think the safty inspection stickers are the best thing we'v got, yea, it cost's $20 per year for the inspection, but you know each and every car is safe ( now the entire inspection sticker is computerized, and goes right to Albany, no more inspecting another car, and using it's sticker ). the '96 and up stuff gets scanned too but, it's not too bad. Shops arn't going to pass a car with questionable workmanship, because if it's bad, it will come back on there liscense.

Well, at least one day a year it's safe.... I doubt unsafe cars cause near as many accidents as unsafe drivers. We had state inspections here back 35 years ago, most of the "inspection stations" used the safety inspection to sell parts and service on a slow day... Just another government approved scam......

Believe this. If you single-flare steel brake tubing and use automotive 45* fittings, the system will split and/or leak. Guaranfreakingtee. Steel tubing is double flared to provide strength, to prevent splitting when the fitting is tightened, and to allow the fitting to seal on the smooth OUTSIDE of the tubing.

However, stainless shouldn't be double flared. The tubing is too hard, and it is strong enough to seal on either a 37 or 45 with a single flare.

Originally Posted by Henry Rifle

Believe this. If you single-flare brake tubing and use automotive 45* fittings, the system will leak. Guaranfreakingtee.

yup.... either brake double flares, or AN fittings is the only way I've ever seen it done.....

Well, in the latest issue of Street Rodder magazine, an article on working with SS tubing this guy is double flaring SS tubing 37* and I thought that was kinda curious because I never heard/seen of this before.

Originally Posted by Hidebinder

Well, in the latest issue of Street Rodder magazine, an article on working with SS tubing this guy is double flaring SS tubing 37* and I thought that was kinda curious because I never heard/seen of this before.

Street Rodder Magazine is NOT always correct. It is written by humans and we make errors. Also, there are some folks who think they know more then design engineers, will try to do it incorrectly. SS is not made to double flare. It is too hard and will split if you try to double it over on itself. You need to use AN style fittings (or specialty fittings like Swage-lok or Parker). CS brake tubing is made to double flare and to use standard automotive fittings. But, it too will split if compressed too tightly at the bend.

An inexpensinve & safe alternative to steel brake lines are coppernickel.

This is NOT copper, and it don't bend heat (or what you call it) which is the big problem and the reason that copper is not allowed as brake fluid pipes.

Coppernickel can easily be double flared.

It would almost be cheaper to go with the stainless and Swagelok vs. using CuNi.

Here in Norway I pay 29$ for 5 meters (197") with 3/16" coppernicel pipe.

There are a lot of options for tubing fittings.You can use a Parker fitting that has a back-up piece that slides over the tube before you flare which reinforces it. I prefer either a Swagelock or Parker ferrule style fitting. They will both excede the required pressure ratings of a brake system and require no flaring. Also when purchasing tubing, make sure that the wall thickness is that which will excede the pressures found in the brake system.