Dick, there is a huge range of steel alloys for both stainless and standard
steel, so it hard to compare without any info of what exact material is
used for either application. However, by handling brake lines myself and
feeling how "easy" they bend, it does not appear that any special strength
steel is used (of course, I am guessing here!). It really feels like cheap
mild steel. Again, I would not be surprised if the pipe stresses due to
pressure are only a very small fraction of the strength of the softest
steel. You need a design factor of 2-3 or so for fatigue considerations,
but beyond that, it may be needless overdesign. If that's the case, it
might be better in terms of long-term safety and reliability to use a more
corrosion resistant material and sacrifice some possibly unnecessary
strength. Also, I would guess that the brake line manufacturers have done
these calculations and tests before they offer a product to the market. On
the other hand, the aftermarket industry in the US is of such low quality,
that mistrust is not unjustified!
Again, there is nothing wrong of being over-cautious, at least till you get
all the numbers and facts in front of you. Especially when you drive one
of these older cars with only one hydraulic circuit.
D^2
At 09:43 AM 6/2/2002 -0700, you wrote:
>I agree that stainless steel is nice stuff to use, but I'm not sure it has
>the same strength as the tubing the OEM specified. I'd tread with caution
>in making any changes away from approved brake tubing. Perhaps someone with
>some strength of materials data would look this stuff up. Problem with
>these descriptions ("copper, steel, stainless") is that we don't know the
>alloy (for steel or stainless) or the heat treat history of these materials,
>and I'm paranoid about venturing too far away from what I know is approved
>for brake service.
>
>Dick Benjamin
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