Listers,
Thanks to all who responded to my request for advice on brake lines. Since
some of them responded to me privately, I thought I'd pass along a summary
to the vintage race list for those of you who may be interested. All
others, hit the delete key now.
Interesting that about half the respondents had flex lines throughout the
car (no hard lines), and about half had hard lines with flex at suspension
points only. The "hard liners" nearly all said that if you use flex lines
throughout, the pedal will be mushy ... HOWEVER, every single respondent who
had 100% flex lines reported that they have a very firm pedal! So I
conclude that the "hard liners" concern is probably misplaced, possibly
because they haven't tried 100% flex lines recently. I'd conclude that
either method works fine.
The only real disadvantage with 100% flex lines, seems to be cost. It is
more expensive per foot. It may be a little heavier, but that seems
insignificant to me. Some people feel that it looks out of place in a
vintage car, particularly a vintage production car. It is, of course,
easier to route through the car -- but must be supported very well. Some
folks feel that flex lines have a life of no more than ten years, and you'd
have to replace it about that often, which again is costly.
For hard lines, the most knowledgeable respondents recommended steel. Hard
lines may last virtually "the life of the car", (not sure what that means in
vintage?) but plain carbon steel could suffer internal corrosion over time,
since most brake fluid is hygroscopic. The tubing is apparently available
galvanized, which would address the corrosion concern. Stainless was
generally felt to be overkill, and may be hard to bend smoothly. The copper
alloys (NOT generic soft copper, as used in fuel lines) were felt to be
perfectly suitable for the job, HOWEVER that may trigger questions &
skepticism by some Tech Inspectors who are not familiar with the various
grades of copper alloy. So, simply in order to avoid a perceived issue at
Tech, I wouldn't recommend copper.
There were several people who recommended specific types of fittings,
flares, etc and I haven't sorted through that yet.
A few people brought up VERY good points about brake line routing
(regardless of whether it's hard or flex): avoid routings that could expose
the lines to damage by jacks, by engine removal/installation, by track
debris or an off-course excursion, or by accidents in general. Also, avoid
the area around the flywheel/clutch (or shield the line), so that if the
flywheel grenades the shrapnel won't slice a brake line. Also, obviously
avoid high-heat areas like exhaust pipes.
Sizes: general agreement seems to be -3 flex for brakes, or 3/16 hard
tubing. For clutch, -4 flex and 1/4 hard (clutch line typically has more
displacement -- i.e. more flow -- than brakes, and much lower pressure).
Thanks for everyone's input, I learned a lot & remain impressed by the
combined knowledge of this list's inhabitants!
Regards,
Mark Palmer
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