The Truth About Copper Brake Lines

"Urambo Tauro" (urambotauro) 02/17/2018 at 12:00 • Filed to: brakes, copper, copper-nickel, rustventures

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A few years ago, I was introduced to the wonderful world of rust-free copper-nickel tubing, for brake lines. I think the stuff is awesome, but how awesome is it, really?

This post originally appeared on December 08, 2017.

Here in the US’s rust belt, the steel tubing often used on domestic cars for brake and fuel lines has a very limited lifespan. It can rust out enough to spring a leak in as little as ten years. Repairing those rusted-out sections (or entire lengths) with new steel tubing can be a bit of a hassle, particularly if you’re !!!error: Indecipherable SUB-paragraph formatting!!! .

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One alternative is to purchase pre-bent lines, but these can be expensive to purchase, delicate to ship, and sometimes even require removal of major components (like a fuel tank) to install.

And if they’re (non-stainless) steel, you can look forward to replacing them all over again in another ten years, just like you would had you fabbed the lines yourself. Sure, you could buy yourself some time by going with with poly-coated steel, but in salt states, that still only buys you a limited amount of time, compared to rust-free options.

If you really want to solve the corrosion issue once-and-for-all (without moving to a more friendly climate), there’s always stainless tubing. But aside from the higher cost (which might actually be worth it in the long run), stainless steel can be finicky to work with due to the hardness of the material. It’s not quite as easy to bend, flare, or seal as regular steel is (not that regular steel is a walk in the park).

Copper-nickel tubing, such as !!!error: Indecipherable SUB-paragraph formatting!!! or !!!error: Indecipherable SUB-paragraph formatting!!! , offers what appears to be a miraculous alternative. Despite being an arguably softer material than steel, it’s DOT approved for hydraulic use. In fact, its PSI ratings are only a little lower than that of steel, still more than strong enough for brake applications, which typically see a maximum of anywhere from 800 to 1,500 PSI. (In some cases, that number can get as high as 2,000.)

But the main attraction here is this stuff’s corrosion resistance. Copper-nickel tubing is rust-free. It does oxidize , but it won’t rust out the way steel does so catastrophically.

If that wasn’t enough of a selling point, the softer material also makes it a dream to work with. It’s so much easier to form, to the point where if you’re careful, you can even bend the tubing by hand without crimping it and causing a restriction. It flares easily, and readily conforms to make a seal when tightened into place.

You do pay for it, though. Depending on where you purchase it from, nickel-copper tubing can run higher or lower than stainless, but always significantly more than cheap ol’ steel. But when you look at the job ahead of you, and the potential lifespan of the tubing, that higher cost can quickly start to look rather negligible.

(Speaking of lifespan, I was surprised to learn that copper-nickel tubing has been used in some European cars since the ’70s! And !!!error: Indecipherable SUB-paragraph formatting!!! for its age.)

Sound too good to be true? You’re not alone. Visit just about any online message board discussing this stuff, and you’ll find folks who are automatically suspicious of using anything softer than steel. They’ll make the argument that it’s just not worth the risk of failure. After all, just imagine the consequences of losing brakes! Or springing a fuel leak!

But when it comes to these discussions, it’s important to understand the material, it’s strengths and weaknesses, and consider its application. Like how some vehicles have wheel bearings that are held in by castle nuts... when it comes right down to it, the entire wheel of the car is ultimately held onto the spindle by... a cotter pin! This doesn’t mean that the car is inherently unsafe, or that the cotter pin needs to be made out of adamantium. There IS such a thing as “good enough”, even when it comes to safety.

And it’s also worth noting that some of these discussions throw around the word “copper” in such a way that makes you wonder if we’re still talking about copper-nickel tubing, or just !!!error: Indecipherable SUB-paragraph formatting!!! , which you do NOT want to use for something like this. The nickel, iron, and manganese content present in the alloy are key ingredients to roadworthiness, improving fatigue (and general) !!!error: Indecipherable SUB-paragraph formatting!!! .

Corrosion particles on an ABS solenoid. Image: Phoenix Systems

But there’s another line of reasoning against copper that caught me by surprise. They call it “copper corrosion”, which has something to do with ions and the metal breaking down from the inside .

At first glance, there doesn’t seem to be a whole lot of information out there about it. It’s something different from !!!error: Indecipherable SUB-paragraph formatting!!! contamination. Unfortunately, articles on the subject range from long-form sleep-inducing technical gobbledygook to what almost comes across like a fearmongering upsell opportunity for shops to increase their profits. Thanks to the limited information available, skepticism about this interior corrosion runs high, especially in !!!error: Indecipherable SUB-paragraph formatting!!! .

But where is the copper even coming from, anyway? Well, as the video above mentions, your “standard” steel brake line isn’t exactly as simple as it sounds. There’s a lot more copper in a steel brake system than just your banjo washers. There’s a copper coating on the inside of the tubing, too.

“...these pipes are made from a 2 layer spiral wrap of steel brazed with a copper brazing alloy. Examination of the inside diameter of a brake line at the braze joint... shows that the copper brazing alloy is exposed to the brake fluid and that a significant portion of the inside surface of the brake line is coated with the copper brazing alloy.”

“...the brake fluid in a typical vehicle is exposed to about [0.12 m^2] of this copper alloy so that copper corrosion rates, well below that required for DOT 3 brake fluids, can result in appreciable copper ion contents in the small volume of brake fluid. ...the inside diameter of a brake line after 6 years of service where it appears that all of the copper on the inside surface and for a small distance into the seam has been removed by corrosion.”

So you can’t escape copper corrosion by using steel. Because of its vulnerability to external rust, steel remains more likely to spring a leak than copper-nickel tubing, despite Cu-Ni’s somewhat lower pressure ratings.

But leaks aren’t the main concern when it comes to this internal corrosion. I can’t find any reports or suggestions that copper corrosion causes brake lines to leak externally. Rather, they all tend to focus on the particles finding their way to the ABS components and wreaking havoc there.

So it would seem that whatever corrosion does take place inside these lines, happens at a much slower rate, and a much smaller scale than the exterior rust that steel lines are prone to. But that relatively small amount is still enough to mess with ABS parts and cause problems.

To combat this internal corrosion, you’re better off turning your attention away from the brake tubing material, and looking at the fluid instead. Brake fluid contains corrosion inhibitors that lose their effectiveness with !!!error: Indecipherable SUB-paragraph formatting!!! . It gets a bit complicated, and a lot of the !!!error: Indecipherable SUB-paragraph formatting!!! goes over my head, so I can’t speak to how effective inhibitor replenishers like “ !!!error: Indecipherable SUB-paragraph formatting!!! ” really are.

But better than any additive, is simply changing that fluid on time, regardless of whatever material your vehicle has for brake tubing. Maybe you’ve already discovered for yourself how AMAZING the brake pedal feels after pushing some fresh fluid through the system after a repair. (That probably has more to do with purging moisture from the lines, than it does with flushing copper particles out, though.) Still, this needs to be part of a regular service, even if it’s not included in the manufacturer’s maintenance schedule. If it’s turned a dark green color, you’re already way behind (come to think of it, is copper where that green comes from? Hmm).

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Need more reasons to keep up on those fluid changes? Reddit’s !!!error: Indecipherable SUB-paragraph formatting!!! has a neglected wheel cylinder for you to look at:

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So changing brake fluid is an important maintenance item, but not the only item if you find yourself in an area where steel lines are prone to rust. No matter how neat copper-nickel tubing is, steel lines are very good at their job too. They just need some extra attention. If you don’t mind getting underneath the car once in a while, take some time to !!!error: Indecipherable SUB-paragraph formatting!!! them off and paint or coat the lines to help keep rust at bay.

But depending on how those lines are routed, access could be a problem. That’s why I prefer these low-maintenance alternatives. All I have to do is keep the fluid clear. And since changing that fluid frequently means cracking the bleeder screws open, there’s less of a chance of those screws seizing up and breaking.

Are there any reasons left to avoid using copper-nickel tubing? Well, maybe impact resistance. If the lines are routed in a vulnerable spot with no mudflaps or shields to protect them during frequent gravel or off-road driving, a random piece of debris could pinch the softer metal.

But as for me, I think this stuff will work just fine. (Besides, it looks cool!)

adamftw > Urambo Tauro 12/08/2017 at 12:06

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I re-did all the brake lines on my Disco with Copper-Nickel stuff.... wasn’t cheap, close to $300 for “pre-sized and flared.” Then I bought a full pre-bent stainless steel kit for my Silverado... it was only $90.

The copper stuff bends like a dream.

Urambo Tauro > adamftw 12/08/2017 at 12:14

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“Pre-sized and flared”- you mean those straight pieces available in different lengths? Better off just buying a bulk roll or two and some fittings (or reusing the old nuts). I’ve seen rolls of NiCopp sell for about $1 a foot (I buy it in 25' rolls).

My bird IS the word > Urambo Tauro 12/08/2017 at 12:21

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I would love to bend the lines myself, for pride. However.... time. I think I am going to split the difference, buy pre-fab stainless brake lines and instead use NiCopp on my fuel return lines, since I can (and have) drive the car without them. That way I get all of the experience, none of the risk of more time without driving.

Urambo Tauro > My bird IS the word 12/08/2017 at 12:26

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Not a bad plan; just make sure you get that stainless to seal up good.

Y’know, another alternative for fuel lines (totally not an option for brakes) is nylon tubing. That stuff’s pretty nice to work with too. (Cu-Ni’s prettier, though.)

adamftw > Urambo Tauro 12/08/2017 at 12:35

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Yes, kind of? They were all essentially “pre bent” except the 2-3 long pieces that were rolled to fit in the box. I didn’t want to deal with flaring and the couple one-off weird flares on the Disco.

My bird IS the word > Urambo Tauro 12/08/2017 at 12:36

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Ahh that nylon would save me soooo much time..... It’s carb fuel return so pressure is negligible. I really don’t need them at all (according to the interwebs) but that kind of stuff bothers me.

Perhaps no line bending for me. But then I don’t learn anything....

Urambo Tauro > adamftw 12/08/2017 at 12:41

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Huh, I didn’t know it was available in pre-bent kits. Neat!

winterlegacy, here 'till the end > Urambo Tauro 12/08/2017 at 12:44

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Wait a second...

Urambo Tauro > My bird IS the word 12/08/2017 at 12:45

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I used NiCopp for the brakes, and nylon for the fuel lines on my truck. The TBI only sees about 13 PSI, but from what I’ve read nylon can handle anywhere up to 40-200 PSI, depending on the size of the tubing.

Urambo Tauro > winterlegacy, here 'till the end 12/08/2017 at 12:47

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OMG

My bird IS the word > Urambo Tauro 12/08/2017 at 12:47

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Well thanks anyway. I wasn’t aware of nylon lines, only the regular hoses and no way those are O.K for underbody stuff.

Urambo Tauro > My bird IS the word 12/08/2017 at 12:50

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Oh, don’t get me started haha. The previous owner of my truck had replaced almost half of the fuel lines with rubber hose. I hear that in racing, you’re only allowed up to 12" of that.

sony1492 > Urambo Tauro 12/08/2017 at 12:56

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I was taught that copper line is not advisable due to the fact that it can’t handle the same pressures as steel lines. (Though to be fair I may have missed something about that in your article.)

Distraxi's idea of perfection is a Jagroen > Urambo Tauro 12/08/2017 at 13:01

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The other thing to be aware of with copper is that being less stiff than steel, it moves around more with vibration, and copper is more prone to fatigue cracking than steel. So if you have long unsupported runs, it’s best to throw some extra clips in. Also if you get a bend wrong, it’s unwise to try straightening it with copper: it work hardens with repeated permanent deformation, which makes fatigue life worse.

(My very first responsibility in my very first job was designing brake lines).

RamblinRover Luxury-Yacht > sony1492 12/08/2017 at 13:06

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Ordinary mild copper is so bad it can be illegal. Copper nickel alloys are WAY stronger and legal everywhere.

RamblinRover Luxury-Yacht > Urambo Tauro 12/08/2017 at 13:08

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A family member recently bought a big stack of it to do a 109 series Land Rover with. Spendy, but the genuine cunifer thick wall stuff, and since it’s British, the supplier also sells girling brake nuts, which are specialty...

Urambo Tauro > sony1492 12/08/2017 at 13:11

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Yeah there’s a chart up there. (TL;DR It’s softer than steel, but still plenty strong enough.)

4200 vs 4500 PSI for 3/16" line, when you’re generating less than half that much pressure...

Urambo Tauro > Distraxi's idea of perfection is a Jagroen 12/08/2017 at 13:11

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The nickel and other ingredients is supposed to help with that but yeah, you still don’t want to go bending and re-bending the same section too much.

Routing it properly is important too. Not just to avoid suspension movement, or to re-use the car’s original support points, but also because of exhaust temperatures. Just the other day, somebody posted a pic of some poorly-installed Cu-Ni on JRitS .

adamftw > Urambo Tauro 12/08/2017 at 13:12

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https://www.summitracing.com/parts/rnb-919-101

I don’t remember if this is the right PN, but it’s what I bought for my Chevy.

Urambo Tauro > adamftw 12/08/2017 at 13:18

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Yeah, I’ve seen the stainless kits. Just not pre-bent Cu-Ni. (Maybe I misread your reply?)

adamftw > Urambo Tauro 12/08/2017 at 13:23

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Here’s the copper kit-

http://www.roverparts.com/Parts/ABP214B

sony1492 > Urambo Tauro 12/08/2017 at 13:26

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Re-read the article and realized you had a whole section breaking down that it’s an alloy, im dumb. Also; Great article.

Urambo Tauro > adamftw 12/08/2017 at 13:30

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Well, how about that. It’s not pre-bent like the steel kits at all, but just like you said- “pre-sized and flared”. Neat.

My bird IS the word > Urambo Tauro 12/08/2017 at 13:46

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MonkeePuzzle > winterlegacy, here 'till the end 12/08/2017 at 17:10

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lol, oppo orange is just rust :D

winterlegacy, here 'till the end > MonkeePuzzle 12/08/2017 at 17:14

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in rust we trust

MonkeePuzzle > winterlegacy, here 'till the end 12/08/2017 at 17:21

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Dr. Zoidberg - RIP Oppo > winterlegacy, here 'till the end 12/08/2017 at 17:26

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My life will never be the same.

winterlegacy, here 'till the end > MonkeePuzzle 12/08/2017 at 17:34

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We’ve gone too deep and we can’t go back.

what have we done

Recovering Gaijin > Urambo Tauro 12/08/2017 at 19:15

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THIS is the correct answer. I > completely < redid the brake system on a ‘52 Pontiac. A 25' roll of NiCopp was $20-ish and easy to work with. DO buy good quality tools for it, tho: not the Autozone flare set. Also a quality small-radius bender from a reputable vendor. You’re doing it once: do it right.

Frenchlicker > MonkeePuzzle 12/08/2017 at 20:25

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Got me a new cover phot now!

MonkeePuzzle > Frenchlicker 12/08/2017 at 20:42

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a qyality use :)

Sweet Trav > Distraxi's idea of perfection is a Jagroen 01/05/2018 at 14:49

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my impression is that nicopp has a thicker wall thickness, and is on par with the work hardening level of the thinner steel brake lines you’d replace it with.

Berang > Urambo Tauro 01/22/2018 at 03:13

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My old saab routes all the hard lines through the interior of the car. Problem solved. Why this isn’t a universal solution amongst car makers, I have no idea.

e36Jeff now drives a ZHP > Urambo Tauro 01/29/2018 at 12:09

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Simple solution to making sure you change out your brake fluid on a regular basis: Start going to HPDEs. For at least all the BMWCCA events I’ve been to the brake fluid has to be less than 6 months old.

Maxima Speed > Urambo Tauro 02/17/2018 at 12:47

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Quality article, My dad and I had been fully won over to the alloy brake lines, for a while now. The advantages are significant for us in the (or on the edge of) rust belt.

Chan - Mid-engine with cabin fever > Urambo Tauro 02/17/2018 at 13:05

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Fantastic piece!

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > Urambo Tauro 02/17/2018 at 13:56

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Hmm I guess that isn’t such an issue in CA, mine are fine on everything. I think my power wagons were all changed because it was in MA, actually you got me thinking about that, I only looked at that briefly. They do seem to be all new.

deekster_caddy > sony1492 03/22/2018 at 16:23

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COPPER lines = no no no

Copper-Nickel lines = YES YES YES!!!!!

sony1492 > deekster_caddy 03/22/2018 at 19:29

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That was 3 months ago

deekster_caddy > sony1492 03/23/2018 at 17:02

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Whoops!

Dude_66 > Urambo Tauro 04/06/2018 at 13:26

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Have nylon brake lines on my Harley, been there for 8 years, no issues, super easy to use

Comis > Urambo Tauro 10/19/2018 at 14:34

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I’m looking to replace the rear hard lines on my car soon and I’m reading this thinking:  W hy worry about the slightly lower pressure capability of Cu-Ni when the pressure capacity of a rusted steel line is a total unknown and is constantly approaching and then going below the pressure capacity of the Cu-Ni line? Sure the steel line starts off better, but as it starts to corrode it’s just going to get worse and worse. Better to have a slightly lower limit with a lower likelihood of corrosion failure.

MickeyDo > My bird IS the word 02/19/2019 at 18:08

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Check Dorman’s catalog.  Make sure you order new fittings too.