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How to Flare Brake Lines for Your Truck Car or SUV

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How to Flare Brake Lines for Your Truck Car or SUV

Created on: 2019-08-21

Learn how to flare brake lines like the pros! Use this technique if you need to replace brake lines on your vehicle!

  1. step 1 :Creating a Double Flare
    • Slide the brake line fitting over the brake line
    • Insert the brake line into the double flare brake line tool
    • Use the flare die to measure the amount of brake line that should be sticking out of the tool
    • Insert the flare die into the brake line
    • Attach the flare clamp onto the tool with the point aligned in the die
    • Tighten the clamp until the die is flush with the tool
    • Loosen the clamp and remove the die
    • Align the point of the clamp with the brake line
    • Tighten the clamp until it bottoms out
    • Loosen the clamp and tool to remove the brake line
    • Clean any burrs in the brake line
    • Repeat for the next end
  2. step 2 :Creating a Bubble Flare
    • Slide the fitting over the brake line
    • Insert the brake line into a bubble flare tool
    • Align the end of the brake line flush with the surface of the tool
    • Insert the bubble flare die into the clamp
    • Align the die with the brake line
    • Compress the clamp until the die is flush with the surface of the tool
    • Loosen the clamp and tool to remove the brake line
    • Clean any burrs from the line end
    • Repeat for the next end

Tools needed for replacement

  • Specialty Tools

    Double Flare Kit

    Bubble Flare Kit

Installation Video
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Hey friends, it's Len here are 1AAuto. Today I want to talk to you about something, making break lines. There's all sorts of different types of flares you can make. You can make a single flare, which is garbage. Don't make that. A double flare, which is very good. And there's also a bubble flare, which is also very good. But there's two different types that you would want to make, the double and the bubble. That's for specific applications of your vehicle. So it depends on what type of application you're working on. Some vehicles require a bubble, you need to use a bubble. Some require the double flare, you'd want to use that. So when you take out your original brake line with the fitting, you'd be able to tell which type to make. Then I'll show you how to make those in a second.

And as always, if you need any parts or tools, you can always check us out at Thanks. So first I'd like to show you how to make a double flare. All right? When you have your brake line, of course your brake lines going to be much longer than this. You'll grab your fitting, put it over your brake line. Once you know you have it over there, you can continue on with your brake flare. I'll take this off of here only because it doesn't need to be on there right now, but we're going to continue with the assumption that it is on your brake line and it's ready to be installed. You've got your a brake line kit. You'll notice that one side of it has a little concave area where kind of dips in before the threading starts and the other side's flat.

You want to put the concave area facing towards the end of your brake line. Okay? We're not going to tighten it up yet because I want to show you this. This is the next tool that you need. It's a little adapter. You want to put the brake line so it meets up with that bottom lip of the adapter. This is a 3/16 brake line, so I'm using the 3/16 hole on my kit and my 3/16 adapter.

You want to make sure that you have that as close to lined up as you can. If it's a little bit over it, that's okay. A little bit under, it's not so good. Now that I have that where I want it, I'm just going to snug this up. Double check it. Make sure it didn't drop down. That looks good. Snug that. Snug that. We're gonna use our adapter tool.

This slides right in there like that. You can see it says 3/16 right on it. Generally speaking, your kit's going to come with 3/16, quarter 5/16. The odds that you're going to need 5/16, 3/8 or a half inch for brake line is pretty much impossible. You'll have a quarter inch or 3/16 as the most common for brake line. So we've got that the way it is.

Next, we have the pressing tool, just slides over like that. You're going to arrest it in there so it's sitting right in the divot. Snug this up. Now you want to take a peak at it and make sure your adapter is sitting level or parallel to the the rest of the tool. If it looks like it's kind of sitting off crooked or sitting off at an angle, you want to just wiggle it around until everything's sitting nice and parallel. That feels good. We'll take this, put it through. We're just going to snug it up until our adapter touches up against the the bottom tool that's grasping the brake line. That feels like it's nice and snug. I don't need to go any further than that.

We'll remove our adapter. Now we've got that pressed in like that. Okay. It's almost like a bubble flare where it kind of comes up a little bit. A bubble flare would come up much higher. Now we're going to take our driving tool, line it up with the hole, wiggle it around a little bit to make sure it's sitting nice and flush in there. I'm just going to go like this until it feels like it bottoms out. I'm not going to keep crushing. Once I feel like it's nice and snug, I don't need to keep going and going until I can't go any further. Okay. It's not about that Hercules. It's Just about pressing it in.

We'll take our tool off here, and there's our double flare. Now you would have your fitting on there. It's going to sit just like this. If you notice you have any little burrs like what you might happen to see on there, you could just take a little piece of scuffing paper or sandpaper if you have some. Just try to wipe it off. Of course, clean it down when you're done. But you'll notice that now this is considered a double flare because it's actually peened over and rolled in, so it's doubled up the thickness of that.

If you were to make a single flare, which is almost the same process, except you don't do the second part, that's what you would have something completely different. This would not work out very well for your breaking system. More than likely, it would leak, and also I would consider it to be very dangerous. This has double the safety, double the thickness. There's no way of that brake line going bad. This would be good to install under the vehicle. This is a double flared end. Now I'll show you how to make a bubble flare.

So now let's talk about a bubble flare. You're going to take your fitting just like before. Put it on your line. That way there you know it's there. You make your whole line. You don't have to worry about saying, "Oh no, I forgot to put on my flare," right? We'll just put the fitting on there. We're going to take our kit. You'll notice this is different than the double flaring kit. It has a much deeper inverted area.

For this, I'm using 3/16 line, which is close to the 4.75. You actually want to line up the line with the top of the tool. You don't want it coming up. There's no adapter that you're going to bring it up to or anything like that. Just bring it up so it's flush with the end of the tool. I always snug up the side that's closest to the line first and then I'll move over to the other side. Snug that up. This is the other end to the tool. The adapters come unscrewed fairly simply. And you can switch it out with whatever size you need. You've got quarter inch and then so on.

I'm going to use 3/16. That's the smallest one. Just screw it right in there. We're going to take our tool. Now we're just going to bring our pressing rod down to where the line is. Make sure it's lining up with the hole and sitting nice and flush. We're just going to drive the tool right down in there, and it'll fit right inside the dimple. Fits perfectly. That just bottomed out right there. I don't need to go any further than that. Bring it back up. Take my tool off of here. Let's loosen that. There's our bubble flared end.

Okay friends, so here's our three different types of flares. In all honesty, I would consider it there to be only two different types of flares, which would be a double inverted flare right here, and a bubble flare right here. This flare right here shouldn't even really have its own category of a flare. This is just kind of somebody who was hoping to make something happen and maybe it worked for a little while, maybe it didn't. But this is very unsafe to make what is considered a single flare.

This right here, like I said before is considered a double flare. It's a double inverted flare. So essentially you take the lining or the outer area of the line, you fold it in, and then you press the whole thing to make the inversion. It's double lined essentially, so it's doubled the strength of something like this, which shouldn't even be there.

But anyway, so this is a double inverted flare. Over here you have a bubble flare. It's considered a bubble flare because it bubbles up. Each vehicle has different specifications on what type of flare you should use. So when you replace your brake line and you take out your original fittings, you'll be able to see what type of flare to make. This is a bubble flare. This is a double inverted flare. Fairly simple to make.

With all that said, I hope that this helped you learn the difference between different types of flares for brake lines. Like I said, you don't want to do that single flare garbage one. Just stick with the double flare, which is the most common or the bubble flare, whichever your specific vehicle calls for.

If it had a bubble, make a bubble. If it had a double, make a double. You're not make a single. Okay? Very important for safety. Brakes are high pressure. Last thing, when you're making your brake line, let's say that you made a nice flare. You're running your brake line all the way down to the other end and you need to make a bend. You just want to be careful when you're bending your brake line not to go ahead and crimp it. If you're making your brake line and you're using steel brake line, it's very easy to crimp. It doesn't like to band and make a nice round curve.

All right? So when you're bending it and you noticed that a peens and it makes like a nice tight curve and it's crimped, just cut it off and start over again. I know it's a pain in the butt, but you need to have brake fluid being able to go into there and back through when it releases. Okay? Super important. All right. Down the road you go.

Thanks for watching. Visit for quality auto parts have shipped to your door, the place for DIY auto repair. And if you enjoyed this video, please click the subscribe button.

Tools needed for replacement:

    Specialty Tools

  • Double Flare Kit
  • Bubble Flare Kit

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