This is a subject that pops up in rec.autos.tech from time to time.
There are 5 acceptable materials for brake lines:
Plain steel seamless drawn tube
Cheap, works OK, rusts through quite rapidly. Most commonly used by
original manufacturers, but not recommended for servicing because the
tube is quite stiff & difficult to bend.
Plastic coated steel
Looks nicer than plain steel, but not really any better for corrosion
resistance. Once the plastic coating is damaged (chafing, spanner
damage or stone chips), the pipe can corrode even faster underneath
the coating. This type of pipe can be difficult to check, as you
can't see the metal.
KuNiFer
Developed as the ultimate brake pipe, IMHO it's a failure. Costs a
fortune, a pain to flare or bend, and it still rusts. It's a triple
layer of copper, nickel & steel, hence the name.
Aeroquip
This is the same Teflon/braided stainless steel pipe used for
flexible pipes to the wheel cylinders. Using it for the entire pipe
run is more common on motorbikes than cars, but it's sometimes done
on competition vehicles. Costs a fortune for little real benefit.
"Copper"
My personal choice for brake pipes. Solid seamless drawn copper,
which is easy to flare, easy to bend & install, and resists both
corrosion & vibration inducing fatigue cracking. It's important to
note that this *isn't* pure copper, but an alloy which avoids the
vibration problems. It's often labelled as "pure copper", but check
that the brand is suitable for brake use.
I can't think of any other acceptable materials. Welded steel tube is
out, as is copper of unknown alloy, sold for air conditioning etc.
This isn't a problem in the UK, as we never see copper pipe for sale
in this diameter anyway, except brake pipe. Fatigue cracking usually
takes place at the edge of the flares for pipe fittings. If you have
a leak from within a brake union, don't just tighten it down more,
but take it apart & check for cracking.
The comments for brake pipe apply equally well to fuel pipe. The only
difference is the diameter, and of course you'll need a different
flaring tool for them.
When buying pipe unions, get brass rather than steel. The price is
much the same, and they don't corrode into the pipe fittings.
Stainless is even better, but costs more.
I make all my own brake pipes, rigid & flexible. having a roll of
pipe & a box of fittings on the shelf means I never have trouble
getting parts, no matter how weird the vehicle. It's also sometime
useful to be able to thread the pipe without a fitting on the end,
then fit the union & make the flare in situ.
Andy Dingley dingbat@cix.compulink.co.uk
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