What is the purpose of the loops in the brake lines?

Question

I am manufacturing new brake lines for my 68 Plymouth Valiant. I am remaking them in the exact same shape as the old ones. This includes the extra loops in the lines. I was wondering wouldn't a straight shot be easier? I'm not planning on varying from the original design but I am curious.

Answer 1

As things change in temperature they change in size.  Different materials expand and contract at different rates.  Look at road - there are expansion joints because reinforced concrete expands at a different rate the earth underneath, and it is at a different temperature.  Further complicating things on a car is the brake lines can be a vastly different temperature the surrounding parts of the vehicle.

The loops allow for differential expansion and contraction without breaking something.

PS: I am a Mechanical Design Engineer.

Answer 2

I suspect that is to eliminate the possibility of a fatigue failure.  The body-on-frame connection in a car is rubber. It moves.  So the brake lines need to move in that area some number of millions of times.  Depending on how that movement happens, a straighter line could fail.

I'm not qualified to give you that answer, though.  You need a mechanical engineer to verify that.