ARB RD40 - Manual (Page 28)

4 Installing the Air System
26
HINT : If the support tube is too difficult to insert, place the
end of the air line into a cup of boiled water to soften
the tubing.
Insert the tube end all the way into the center compression nut.
Screw on the outer compression nut and tighten. The ferrule and
support tube are now permanently attached.
Assemble the support spring over the outside of the outer
compression nut.
Secure any loose sections of tube with a cable tie.