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Question was asked in 2006 about why people put loops near the connection ends of brake tubing: The answer is still important, so please let me refresh. It has little to with vibration isolation or thermal expansion. It will certainly INCREASE the tendency of the tube to vibrate and could therefore, in principle, lead to failure. Thermally, if heated from end to end with a torch, the tube could lengthen a fraction of an inch (e.g., heat a steel tube 60 inches long to 500F and it will get about 0.21 inches longer -- I wouldn't panic over that.), which is easily absorbed by other flex points in the pipe.
The LOOP has to do with ease of replacement if the fitting goes south. Historically it is called a "service loop" and is there for service reasons, as the name indicates. It can also come in handy if you are using tubing that has flares already made on both ends. If you get to the end of the run and have a few inches of tube left over, coil-it up. Easier than cutting and making a new flare. Of course, some people secretly think it makes the thing look more "racey".
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