View Full Version : Brake lines and fittings

12-13-2002, 10:15 PM

I'm rebuilding the brake system on my TR3A. While removing the brake lines from the master cylinder, I snapped the line. As I was turning the fitting, I was tearing the brake line because it had corroded to the fitting. When I reassemble everthing, can I use anti-seize or some other product to prevent this from happening again? What about something on the threads to make future dissassembly easier?

Safety Fast,

12-14-2002, 04:31 AM
Hello Dave,

Not original I know, but I always use copper brake pipes and brass unions, so there is not the same corrosion problem as with steel. I can't think of anything that will prevent steel pipes and unions rusting together, unless you regularly douse them in an anti rust treatment. (Wax based)
Good luck,

Alec graemlins/thirsty.gif

12-14-2002, 07:22 AM
There may be copper *coated* steel lines available for this purpose (I know they do this with other forms of steel)....but I'm not sure I'd use pure copper lines; an ordinary car (even an old Triumph) can develop 1500 psi + in the brake lines...this would probably cause "yield" in copper. I *was* wondering if stainless steel lines were available (maybe from "Earl's Supply" or other race car distributors)? Worth looking into...
Anti-seize on the thread and between the coupling and brake line would be OK.....obviously, keep it away from the flare surfaces (where the line seals) and be sure it doesn't get in the lines. A little dab of silver/aluminum paint around the ouside end of the brake line (where it contacts the coupling) might also keep corrosion at bay.



Earl's doesn't seem to have these, but there are lots of others who sell stainless steel (304) solid and flex brake lines...type into "Google" for a complete list...Brit-car brake couplings are pretty ordinary, so you should be able to find something in an appropriate length, even if the company doesn't list a "Triumph" kit...here's one place that may be able to help:



[ 12-14-2002: Message edited by: aeronca65t ]</p>

12-14-2002, 01:48 PM
Hello Aeronca,
Well, I have used pure copper lines for a very long time; they are sold here in the UK as kits for most cars. (I do have my own flaring kit so make my own anyway.) I'm sure that they would not be sold if they were not up to the service required, but they do need closer clipping than steel to eliminate vibration.
I feel happier with a non corroding line rather than steel which gets weaker as it rusts, especially as it is very difficult to inspect every part of the line.
I see that you say stainless lines are available, but I'm surprised that it is ductile enough to flare? I do use stainless braided flexible hoses though.
BTW, my Triumph fittings are 3\8" UNF thread.


[ 12-14-2002: Message edited by: piman ]

[ 12-14-2002: Message edited by: piman ]</p>

12-14-2002, 03:56 PM

I think I’ve figured out the difficulty here.

We’re talking about different things.

As I said, I wouldn’t use “pure” copper lines…..and I absolutely wouldn’t.

The SAE and the S.I. (which all the EU countries follow) requires brake tube to be built with a max working pressure of about 3000 psig and a safety factor of about “6” (depending on diameter). This means an ultimate bursting strength (yield point) of about 18000 psig (6 X 3000). Ordinary copper tube has a yield point of about 4000 psig (in smaller diameters) so it would never pass this standard (based on this rule, it would only be good to about 670 psig). Carbon steel tube in small diameters has a bursting point of about 19000 so it works out well in this application. But I agree that it has corrosion problems that can be exasperating.

Then, I looked further and discovered that brake tubing is available in “copper-nickel alloy”. Whole different matter! *This* stuff has a bursting pressure of about 17500 psig so it apparently passes the S.I. test. And there are kits available with this alloy. Here’s one:


I guess what I have to say is that I *hope* this is what you’re using, and not “pure” copper. Here’s an engineering study on “copper-nickel alloy” and it’s properties (sounds like good stuff).


A nice discourse on cu-ni tubing (with a *warning* about using ordinary copper tubing).


As for flaring 304 stainless, it’s done the same way as carbon steel; using a double flare swaging tool (as I assume you’re using also).

Dave...have we overloaded you with "brake tube" info?


12-15-2002, 06:26 AM
Hello Aeronca,

Your last reply got me thinking so I had a quick look at the supplier's website (www.automec.co.uk)
and it does refer to both copper and copper nickel. The 3\16" brake line is sold in copper at 20 s.w.g while the copper nickel is 22 s.w.g., so there is a wall thickness issue.
I'm not too well up on stainless grades but my limited experience of working with stainless is that it is hard and difficult to manipulate. The flare (Yes my flare is a double flare) streches the material quite a bit.



12-28-2002, 07:18 PM
In addition to Automec brake lines they come pre measured for each marque application.compleat with instructions and they are numbered you can't go wrong with these.I used them on my Sprite restoration.Worth every nickle! available through Moss.

74 MGB graemlins/yesnod.gif

12-31-2002, 05:58 PM
Aloha All,

Thank for the input. I've made the replacement from steel brake line from NAPA. I've decided to use copper anti-seize on the treaded fitings. I put some anti-seize on a rag and then carefully wiped some on the threads making sure none got on the brake line itself. After the brakelines are connected, I used some RTV sealant around the top of the fitting to keep moisture and road grime from getting down between the fitting and brakeline.

Safety Fast,