Copper-nickel brake lines are the go-to upgrade when rust is the problem. They don't corrode the way steel does, and you can bend them by hand. They aren't the right call for every job, though. Steel lines cost less and have a higher burst rating, and on a lot of trailers they're all you need. Here's how the two compare and when each one makes sense.
Copper-nickel vs. steel vs. stainless: quick comparison
| Copper-nickel | Galvanized / coated steel | Stainless steel | |
|---|---|---|---|
| Corrosion resistance | Excellent. Won't rust. | Good while the coating is intact. Rusts once it's chipped or worn. | Excellent |
| Burst rating | High. Well above brake system pressure. | Highest at the same size | Very high |
| Bending | By hand. Easy to route around frames and axles. | Needs a tubing bender for clean bends | Stiff. Needs a bender and patience. |
| Flaring | Flares cleanly with standard tools | Standard tools | Hard to flare and seal. Often needs a heavy-duty flaring tool. |
| Cost | Higher | Lowest | Higher |
| Best for | Salt, boat trailers, long service life, tight routing | Most trailers, budget repairs, OEM-style replacement | Show builds and maximum corrosion resistance where tooling isn't an issue |
What copper-nickel brake line is
Copper-nickel brake tubing is a 90/10 alloy: about 90% copper and 10% nickel, with small amounts of iron and manganese for strength. The alloy is designated UNS C70600. It's sold under names like "NiCopp" and "cupronickel." It is not the same as plain copper tubing. Never use plain copper for brake lines (see the FAQ below).
It isn't new. Volvo started using copper-nickel brake tubing in the 1970s, after vehicle inspections in Sweden showed a high rate of failures from corroded steel lines.
Where copper-nickel wins
Corrosion resistance
This is the main reason to choose it. Copper-nickel doesn't rust. In cyclic corrosion testing that combined salt spray, humidity and mechanical abuse, steel tubing passed the 60-cycle minimum but failed well before 120 cycles. Copper-nickel completed 200 cycles with essentially no loss of strength. If you run your trailer through road salt every winter, or back it into salt water, that difference decides whether you replace your lines once or every few years.
Easy to bend and install
Copper-nickel is soft enough to bend by hand. That makes it much easier to route along a trailer frame, around crossmembers and up to the axle. You need fewer fittings and less tooling, and there's less risk of kinking a line you've already flared. It also flares cleanly with standard double-flare tools.
Where steel still makes sense
Cost
Galvanized or coated steel tubing costs less per foot than copper-nickel. On a long trailer run or a fleet of trailers, that adds up. For trailers that don't see much salt, steel will last for years.
Burst strength
At the same diameter, steel tubing has a higher burst rating than copper-nickel. In practice, both have tested burst pressures far above what a hydraulic brake system produces, so either is safe when it's installed correctly. Steel's extra margin matters most on heavy-duty applications and where lines are exposed to impact.
Rigidity
Steel holds its shape. On long unsupported runs it's less likely to sag or move. Copper-nickel needs to be clipped and supported along its length, which is good practice with any brake line.
What about stainless?
Stainless steel resists corrosion as well as copper-nickel does, and it's very strong. The tradeoff is installation. It's stiff to bend, it work-hardens, and it's hard to flare well enough to seal reliably with inverted-flare fittings. Unless you have the tooling and experience, copper-nickel gets you the same corrosion resistance with much less hassle.
Which should you use on your trailer?
- Choose copper-nickel for boat trailers, trailers that see road salt, equipment you plan to keep for a long time, or any job where routing the line is the hard part.
- Choose galvanized steel for budget repairs, like-for-like replacement of existing steel lines, and trailers that stay mostly dry.
- Either way, use inverted-flare fittings in the correct size, support the line with clips, and bleed the system completely after the install.
Shop brake tubing coils, pre-cut straight tubing and inverted-flare fittings, or see our complete hydraulic trailer brake kits. Running air brakes on the tow vehicle? Read how air-over-hydraulic brakes work.
Frequently asked questions
Are copper-nickel brake lines better than steel?
They're better at resisting corrosion and easier to install. Steel is cheaper and has a higher burst rating. If rust is your problem, copper-nickel is the better choice. If cost is the main concern and your trailer stays dry, steel is fine.
Are copper-nickel brake lines safe?
Yes. Properly made 90/10 copper-nickel tubing has a tested burst pressure far above the pressure a hydraulic brake system produces. OEMs have used it for decades.
Is copper-nickel brake line DOT approved?
DOT doesn't certify brake tubing by brand the way it certifies brake hoses under FMVSS 106. Copper-nickel tubing made to SAE specifications for hydraulic brake systems is legal to use and is installed by OEMs. Buy from a supplier that states the alloy and spec.
Can I use regular copper tubing for brake lines?
No. Plain copper tubing hardens and cracks under vibration, and it isn't rated for brake system pressure. Only use copper-nickel alloy tubing made for brake lines.
Do copper-nickel lines need special fittings?
No. Standard inverted-flare tube nuts work. Copper-nickel is softer than steel, so tighten to a firm seat and don't overtighten the flare.
Can I connect copper-nickel lines to existing steel lines?
Yes. Join them with a union of the correct size and thread. A common approach is to replace the corroded sections with copper-nickel and leave sound steel lines in place.
How long do copper-nickel brake lines last?
Because they don't rust, they typically outlast the trailer's other brake components. In accelerated corrosion testing, copper-nickel ran 200 cycles with essentially no loss of strength. Steel failed before 120 cycles.
Not sure which tubing fits your build? Contact us and we'll help you spec it.