Why do we air down?
 

How about we start with this image?

http://www.ausjeepoffroad.com/forum/...1&d=1400549906

Airing down your tyres on your Jeep is the easiest and single best thing you can do when your about to go off road. Whether your driving on sand, rocks or a dirt track, simply reducing your pressures can increase your footprint on the surface dramatically improving your traction.

The most common way of reducing your tyre pressure is with a tyre deflator. This ensures all tyres are down to the same PSI.

First lets talk about Sand:
As we drive on soft sand, we create a bow wave around and in front of our tyres. Reducing your tyre pressure, will also increase the size of this bow wave width wise, but it will also increase your footprint on the sand improving traction and using more of the tread surface of the tyre.

One of the big things to remember when driving on sand with lower tyre pressures is that if you go to low e.g. below 15psi without have some form of beadlock on your rims, you could risk rolling a tyre off the rim. This could happen by turning erratically or sharply.

Next time we will talk about driving on ROCKS with lower tyre pressures.

Why do we air down?
 

jimmyb, need to add to this discussion the 17" and 18" tyres that are now coming onto the market with the newer Jeeps. Advice I've been given for my WK2 with 18" tyres is to not go below 20psi due to the smaller sidewall.
I have installed a higher BFG ATKO which gives me some scale, but accept that I am limited in how low I can go and drive accordingly.

As we see in the first image, this is a recommendation for a 15" rimed tyre.

What pressure do you run your 35's at for road use Jimmy?

Very useful thread thanks. Comes in handy for us noobies:D