Copper pipes

[Rust bucket]

Hi all, just looking at Brake master cylinder comments about if it's worth rebuilding them, then seeing copper brake pipes mentioned as possibily dangerous . I bought a copper brake pipe kit on line and it looks to be well made with neat flaring at the pipe endings and letters and numbers printed on the pipes as follows, 3/16 OD 22 SWG BS EN12449 P1160 are these safe to use?.

[simmitc]

The concern over pure copper is that it "work hardens" over the years and may eventually fracture. A copper alloy such as "Kunifer" is vastly superior. That said, a major supplier of brake components sells pure copper and insists that it is suitable. With product liability, if there was a problem with the copper pipes, then all the traders would stop selling it. Pipe made to the correct British standard should be fine as long as it is secured properly so that it cannot move around. The only place on a Minor where the pipe will flex very slightly is where it is connected to the rear wheel cylinders, which slide up and down. However, the risk is largely theoretical. There will be some people who have suffered from fractured pipes, and other who have had the same pipes for years without any issues. You have to be aware that brakes are a major safety critical component that must be in working order. The car will pass an MOT with copper pipes, so VOSA thinks that the pipes are safe; but if you are concerned, then send them back and buy a different type.

[MarkyB]

Pinched from some web site;
EN Alloys Numbering System
The system uses 6 characters.
The first character is a C for Copper-based alloys.
The second character is a letter from the table below.

The third, fourth and fifth characters comprise a 3-digit number, which with a sixth character (a letter) indicate the alloy group. These number series and corresponding letters are also shown in the table below.

An example is CW614N.

Character/Digits Key
B Ingot for re-melting to produce cast products
C Cast Products
F Filler Materials for Brazing and Welding
M Master Alloys
R Refined Unwrought Copper
S Scrap
W Wrought Products
X Non-Standardised Materials
000 to 099 A or B Pure Copper
100 to 199 C or D Copper Alloys with less than 5% added elements
200 to 299 E or F Miscellaneous Copper Alloys with more than 5% added elements
300 to 349 G Copper-Aluminium Alloys
350-399 H Copper-Nickel Alloys (Cupro-Nickel)
400 to 449 J Copper-Nickel-Zinc Alloys
450 to 499 K Copper-Tin Alloys
500 to 599 L or M Copper-Zinc Alloys - Binary
600 to 699 N or P Copper-Zind-Lead Alloys
700 to 799 R or S Copper-Zinc Alloys - Complex

[bmcecosse]

The work hardening happens at the rolled over end - I had a pipe (came on the car when I first acquired it) just come away in my hand - leaving the bell-end inside the wheel cylinder. Far better to use Kunifer and have no worries.

[Rust bucket]

Okay thanks all, after a year or so I will replace the pipes at the rear which could be subject any movement. )

[dp]

I haven't had a standard back axle for 20+ years so don't know exactly how the brakes fit together. That said, if the slave cylinders move in use shouldn't there be a flexi hose between them and solid pipe on the axle? Seems a risky design if the movement of the cylinder is taken up by flexing of a solid brake pipe whether steel, copper or cunifer?

[MarkyB]

Once the brakes are adjusted there won't be any movement, as they go out of adjustment there may be a little.
The straps that hold the solid pipes should be fitted about half way between the diff and brake (from memory) if they are fitted too close to the brake any movement will be concentrated on a shorter run of pipe.