If you’ve never worked on your car’s brakes before, you might be thinking: “What is a flare?” “What is a double flare?” “What does a flare have to do with the brake system anyway?” If you’re not a mechanic, the lingo might completely miss you, as this kind of technical jargon is not heard commonly when you hear laymen referring to brake jobs.
So do brake lines need to be double flared? Double flares are necessary for brake lines due to the high pressures inflicted on them by the hydraulic system. Single flared lines are only appropriate for low-pressure lines due to their tendency to crack or leak. The brake system cannot afford to have a leak in the lines since this can cause serious injury or death if the brakes fail.
What is the difference between single flared lines and double flared lines in a vehicle, and how do they affect your brake system? Read on to find out more about double flared brake lines and why they’re so important when fixing your brakes.
Single Flared Lines vs. Double Flared Lines
While some single flared lines may show up on cars that have been incorrectly repaired by a shade tree mechanic, a double flared line is the OEM standard for automotive braking systems and, as such, is a much safer option in the brake system to avoid any kinds of leaks or other pressure-related issues.
Here are some of the various flared lines you might see in your car’s braking system:
- Single flared lines: While you might run
into single flared lines in an automotive design elsewhere, you should never
see them in the brake system unless someone has gone into repair the brake
system and not put it back together correctly. Single flared fittings should never
be used on steel brake lines.
- Double flared lines (SAE): These are the
type of brake line fittings that are most commonly found in American and Asian
models of vehicles. Double flared lines help control friction wear and cracking
at the sight of the flare that can ultimately lead to a leak in the line.
- Bubble flared lines (DIN): These line fittings are more common in European models but are considered equal in safety to a double flared line when they are used in high-pressure systems on a vehicle.
The bottom line is that whether your car has SAE brake line fittings or DIN brake line fittings, it should never have single flared brake lines. This is because single flared lines are a significant safety hazard in a car’s braking system.
Why Are Single Flares Bad for Brake Lines?
The reason that single flared fittings are such a big no-no when putting your brake system back together is that a single flared fitting almost always tears the metal during the fitting and creates a chink in the brake line. Even if the flare does manage to hold a seal, there is still the chance of a blowout at that point in the brake line from that point on.
This is the reason that the Department of Transportation outlawed single flared brake lines, which means that you shouldn’t install them on your vehicle even if you wanted to.
If your brakes fail and kill someone, the DOT will disassemble your vehicle looking for flaws like this, and installing an aftermarket single flared brake line can lead to a manslaughter charge if you’re not careful and obey the law.
Liability aside, brakes are no joke, and you don’t want to skimp on one of the most crucial safety systems in your entire vehicle.
If you don’t have a flaring tool to create double flared brake line fittings, either get one at an auto supply shop or have your car worked on at a real mechanic who has access to a flaring tool so that your brake lines are both safe and in compliance with the law.
What Is a Brake Flaring Tool?
A brake flaring tool is a tool that is used to create a double flare on the end of brake line fittings in order to create a more secure link between pieces of the brake line. This is crucial in a high-pressure system to preventing both leaks and blowouts when the system is under load (i.e., when the car is being operated in extreme temperatures or weighted conditions).
Flaring tools are one of the oldest types of tools in metalworking and have been used by pipefitters for hundreds of years outside of the automotive business.
That means that the technology has been refined to the point that even laymen that don’t have a ton of experience in auto repair can still use it fairly easily and create sound, safe fittings to go on their automotive systems.
When a brake line is flared, that means the end of the metal line is stretched out enough that it can be fit together with another section of metal line without there being any break between the two lines that could constitute a leak or a point of weakness that a high-pressure system could eventually exploit.
Brake flaring tools can be purchased either through an automotive supply store such as AutoZone, or they can be purchased online through various vendors. It is vital that you know how to correctly use a brake flaring tool before taking it to your car to avoid causing damage to the brake system because of a lack of knowledge.
Without the proper know-how and experience, tou could cause issues with your brake system that could lead to a total brake failure later on down the road.
What Lines Can Be Used with a Single Flared Fitting?
In automotive applications, the only lines in the car’s system that are safe to be used with single flared fittings are the coolant and fuel lines. These lines are usually constructed with single flared fittings because single flared fittings are cheaper and easier to manufacture on any lines that don’t run a high-pressure system.
If you end up leaking either coolant or fuel as the result of a failed single flared fitting on your coolant or fuel line, this is usually a much smaller problem and a less complicated repair than if you are leaking brake fluid.
This is a scenario that puts not only the driver and passengers at risk, but also anyone in the area surrounding a car when it loses the ability to brake.
If you lose all your coolant, your car will simply overheat and stop running. In the worst-case scenario, you might overheat and damage your engine.
But this is still significantly less serious than if you lose all your brake fluid in a blowout and learn that you don’t have any braking power when you’re coming up to a stop sign at forty miles an hour.
Use Double Flared Fittings on Brake Lines—It’s the Law
Regardless of how you personally feel about how important it is to use double flared or bubble fittings on a brake line, the fact of the matter remains that it is both objectively unsafe and illegal to use single flared fittings in a brake system.
It might cost you a bit more on the front end to invest in a flaring tool that can create double flared fittings for your brake system, but it’s a whole lot less expensive and complicated than trying to recover from a catastrophic brake failure while you’re out on the road.