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Hard Lines vs. Soft Lines

Standard air suspension setups are normally equipped with flexible nylon air hoses to supply compressed air to various parts of the air ride setup.  The next aesthetically pleasing upgrade readily available for the standard soft air hose lines are by fabricating “hard lines” out of metal pipe.

Metal piping has been used in vehicles for  many decades now as fuel lines, brake lines, oil return lines, etc… so why is the safety of these air lines being called into question by some of our Forum members?  Putting the cost factor aside for a moment, the questions being raised suggest that certain metals used in “Hard Lines” in air suspension setups are unable to tolerate both the constant high pressures of the compressed air and high vibrations of being daily driven in the trunk of a car.

eight08customs began the debate by stating that the best  way to run air lines is by using softer PVC lines:

They’re all good.  The rubber ones arent rubber, but PVC and only use DOT apporoved lines.  Anything that’s not DOT approved shouldnt be used in automotive applications.  Also only use DOT approved fittings. From that first set up with the PVC lines those fitting with the blue ends, unless they are stamped with “DOT” I wouldnt use those.

The metal lines IMO from experience aren’t the safest thing out there becuase they crack very easy from vibration. It looks nice/ easy to bend/ and cheap, but cracks easy.

Stainless is the way to go becuase it will hold to to more pressure and vibration.  Its actually used for very high pressures in HYD systems. It cost a lot and needs stainless steel cutter and is hard to bend.

[email protected] stated that in his experience, copper air lines are one of the less expensive options but are also highly safe:

My Experience – Nothing but success! I will agree stainless is not easy to work with and does cost $$$$!

I have not yet ever seen a line fail do to vibrations, there are a lot of hard tubing in a car IE: brake, fuel, oil return lines, tranny lines, air conditioning etc.

My 1952 ford F1 fuel lines are all in copper and original 60 years old, no leaks.

Funny how 2 different people can have different views on the same subject.

eight08customs rebutted with the fact that copper air lines are not DOT or FAA approved:

1. Copper lines are not DOT or FAA approved. You will never see copper lines installed on any cars or Semi trucks, busses, trains, planes and boats these days. I have seen many times Copper lines used on old cars fuel lines but never in Brake lines. If copper was so safe why isn’t it used in Air Crafts for Fighter Jets?  Why doesn’t the DOT Approve copper lines in Semi Trucks or Busses?

2. Copper is also the softest metal. You’re right about cars having a lot of hard lines. I have seen all of them fail in some sort of way by rubbing, vibrations, smashed because of improper routing.  Nothing is forever, but the real question here is what is safer and what is DOT Approved?

From what we’ve been able to research, the US DOT has approved Stainless Steel brake lines but has not approved Stainless Steel or Copper air lines.  Does this mean that it is completely unsafe to use Stainless Steel or Copper tubing in your air ride setups?

The answer is more complicated than a simple “yes” or “no” because each person must take their own safety and responsibility into their own hands.  It is true that there are vehicles in existence that have been running Stainless Steel and/or Copper air lines for long periods of time without fault, however is this due to expert installation and properly secured tanks and lines or is it due to the fact that the metals are able to withstand the constant bending and vibrating movement with ease due to their composition?

Join the debate in the AIRSOCIETY Forums and become informed about this subject before you make the leap.

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