The following SAE specification, J512 APR97 shows the torque table for the nominal size fitting with a SAE double inverted flare. Through our internal tests we believe the following SAE specification is correct when the matting seat is brass. We have proved out both steel fittings with steel tubing as well as stainless steel fittings with stainless steel tubing. The results showed an almost exact concentric impression into the brass seat with both materials. But, this has been proved out using components with new seats. Master cylinders, wheel cylinders, flex hoses, unions, distribution blocks, proportioning valves, metering valves are all made from either brass, steel, cast iron or aluminum. So the torque table would be used as a guide. It would be up to the installer to verify the torque needed for sealing the associated materials to achieve a proper seat but without deforming the seat to a point where it won’t seal or striping the threads. Keep in mind the use of original or used components that have already seen a tube installed and the seat formed to the old tubing will need additional torque to overcome the previous impression in the seat to properly seal the new tubing.

SAE J512 Revised APR97
NOM Tube OD ( In.) Torque Requirements
for Steel Nuts (N-m)
Torque Requirements for Steel Nuts (lb-in)
1/8 6.8 5
3/16 13.6 10
1/4 16.9 12.5
5/16 20.3 15
3/8 23.7 17.5
7/16 33.9 25
1/2 45.2 33.3
5/8 56.5 41.6
3/4 73.4 54.2

We ship the line in an oversize box approximately 10″x18″x66″ (the largest allowable by FedEX) with a shipping bend in the center section. This shipping bend is easily removed by placing the line on the floor, holding one end against the floor and pressing your hand slowly along the bend to straighten it out. No need to use tools.

The stainless steel nut will require approximately 15 lb./ft. to seal. This is slightly more than the normal steel nut requires. Remember to check the seat where the flare will seal. If the seat is deformed you may need a new block, hose etc.

Stainless steel tubing, nuts and gravel guard are impervious to salt and other metal-destroying elements your vehicle is subjected to. Equally important is that it will never change its appearance. It is a permanent replacement that looks great.

Stainless steel fittings will not rust. Which means that if you need to remove them they are not rusted to the brake line and come off as easily as they went on.

Anti-seize and Teflon tape are not needed when installing your lines. The seat on the end of the tube is what seals against the brass seat in your cylinder or block. Make sure the seat is the correct size and has not been damaged.

Yes, we can reproduce almost any line in OEM steel or in stainless steel working with the original lines or from wire or soft tubing templates.

Yes, we need the original line to work with.

No we don’t sell systems, we only carry straight length tubing, 90°, 45°, 15°, 180° J-bends and 180° U-bends for the customer to fabricate exhaust systems by themselves.

Our Corporate Offices and factory are located in Lancaster, New York; a suburb of Buffalo, New York.

Our Quality Control department oversees the manufacture of all flare ends both inverted and bubble, the specifications we adhere to have been set by the Society of Automotive Engineers – SAE.

Unless otherwise specified, shipping is FedEx. The cost is determined by your address.

Most of the popular cars and trucks are in stock. The more unusual vehicles we will manufacture to order.

Our lead time is determined by several factors. First, we check to see if it is in stock. Items in stock will take 3-5 days to ship. If it is not in stock, we need to make to order. We check to see if we have a pattern. We have over 20,000! If we don’t, we check to see if customer can supply a pattern (old lines in good condition) or blueprint. Lead time on custom or non-stock orders is determined by the season and the amount of orders pending ahead of yours.

Sorry, we do not include clips, however we do carry generic line clips that can be substituted for the factory clips.

96″ is the maximum that can be shipped straight. We recommend that a shipping bend be used to reduce the shipping cost.

The diameter of the tubing to determine proper pressure and volume for fuel related tubing. This becomes an issue when plumbing the vehicle after a new engine installation, when the components have changed; displacement, intake size and style, fuel pump and carbureration. In our experience, there is a tendency to use too large of a diameter when it’s not warranted.

Corrosion is the biggest problem so replace them before there is a failure, which could be very dangerous. Heat is another issue, so determine where the heat sources are before replacement. Boiling fuel or brake fluid can cause serious problems and be hard to track down.

There are two indicators to determining when to replace tubing: The most obvious is when you perform a visual inspection of the exterior of the tube and find corrosion in the form of rust. Some locations that you should inspect are under the clips that hold the tubing to the chassis and at the ends behind the fittings, as the ends are usually susceptible to more damage and moisture especially at the wheels and where the tube attaches to hoses. The second is more difficult to identify. Brake fluid is hydroscopic, so it absorbs water at a rate of 2 percent each year. This also lowers the boiling point dramatically. Without regular flushing, the water will start to attack the inside of the tubing. Since the OEM steel tubing has corrosion protection on the outside only, the tubing has no protection on the inside diameter. When bleeding the brakes and finding rust colored fluid, you will know that the lines at are the point of deterioration to the inside of the tubing.

If there is any corrosion? Never. For the simple reason that if corrosion has started and one tube has failed, more than likely the rest of the system is compromised. Never use a compression union. This method to prohibited by the DOT. Otherwise, you can join an old line to a new line.

Typically when joining tubes, Classic Tube strongly suggests using a brass union, this will cut down on the potential galling of the threads as well as give a nice soft seat for the tube flare to seal against. No issue with steel to stainless, but never use an aluminum fitting without some anti-seize( only on the thread).

The key will be the successful disconnection of the old tube. Things to take note of: The tube nut is seized and/or the hex starts to round; The nut is seized to the tubing and starts to twist the tube when unscrewing. Those are indicators that it’s time to install a new tube. When trying to reconnect an old tube with potential fatigue, you can compromise the torque value to reinstall the tube properly and to achieve the correct seat pressure and seal.

There are numerous ways, just try to use common sense. One this is for sure, heat is the worst thing to be routed by.

Moving parts like parking brake cables, throttle linkage, cooling fans and clutch linkage can become an issue. Look at the range of motion in each moving component that might not be evident in a static position.

Starting in the 1950’s, manufacturers used a fiberglass sleeve with an asphalt coating to cut down on heat transfer. Around this time, OEM’s would ”sleeve” the outside for the tube to create a double walled tube in areas most susceptible to shock, vibration or damage. In later production models, the use of spring guards or armor guard was used to combat “sand blasting” of the tube by road debris. This was installed strategically in certain areas of the tubes that would see the most potential damage. Classic Tube uses all of these in our manufacturing process to duplicate the OEM component. Classic Tube also sells these items separately for the “do it yourselfer.”

The best material is stainless steel, since it is the least prone to corrosion. The second best goes by multiple industry names but is a steel tube with a top coating comprised of 95% zinc and 5 % aluminum with an aluminum rich epoxy topcoat then topped with a polypropylene cover. Readers will be most familiar with the third type since this has a greenish color to it, which the OEM’s started to use in production cars in the mid 80’s. The earlier cars used Tinned Bundy Weld. Most people will be familiar with this term. This is the tubing that has the galvanized silver look that was used from the 30’s to the 80’s. All automotive manufacturers have a specification for the tubing they use on current production and it must pass a minimum required time in a laboratory salt spray test.

When replacing old tubes with a new preformed replacement it’s good to always match up to the original so as to aid in visualizing the reinstallation and identify any obstacles.

A common misconception is that stainless steel tubing cannot be double inverted flared. Since there are many different grades of stainless steel there are some grades that will not form. At Classic Tube we use USA made, annealed stainless steel tubing: A grade that is specific for bending and flaring.

Another misconception is the use of Teflon tape. We only use tape on pipe thread. In a flare nut installation, the threads are doing the compression of the flare to the seat.