
Airing down is part of 4-wheeling. At the start of the day, everyone sits beside each wheel, patiently letting the air out of the tyres until they are soft enough to increase the amount of surface area on the ground (and therefore increase traction)
To make life easier, Neville came up with these nifty tyre deflators - hose clamps that you just clip on, letting the air out without having to hold something against the valve. They even have an end the same size as a valve so that you can check pressure easily by holding your pressure gauge againt the end.
More than two of these are impossible to manage, they let the air out too quickly.
Got a set of Staun deflators for Xmas, these are very cool but $2 hose clamps are way more cost effective!
Found on: http://home.off-road.com/~landy/index.html