SEE THE PHOTO FOR A REPRESENTATION OF THE DIFFERENCE AIRING DOWN MAKES TO YOUR TIRES AND TRACTION PATCH: (Result may vary)
We air down in the summer to increase our traction on loose dirt and rocks but also to smooth out the rough and bumpy trails. We often air down to 15 pounds or so for these summer rides. However, on winter snow runs we may air down considerably more. OK...a LOT more. On our trail ride this weekend, we had a good number of people new to deep snow wheeling. That is, wheeling in/on 2-3-5 feet or more of snow. Most often, our greatest challenge in helping these new people with the skills to do this is getting people to lower their tire pressure enough to allow them to ride on top of the snow. Cutting through is fine for a foot of snow, but 3 or more feet and you need to be on top. Note: This technique is great for “packable” (think: good snowball type snow) snow but is not as effective, though still far better than full air pressure, in powder.
Let’s face it; we all grew up being told that having your tire pressure below 30 pounds or so will result in some kind of tire catastrophe. And here you are being told to lower your pressure much, MUCH lower than 30 pounds. Just to be clear, while bead locks are nice to have, very few of us have them so I am speaking about using pretty much standard, everyday wheels, and off-road-ready tires though some combinations are better than others. Of course, we are not talking about running these ultra-low pressures on paved roads or at any kind of normal road speeds. We are only talking about driving deep snow covered trails so think more like 10 to 15 mph is at the very TOP of the speed scale.
Eventually, on this last trip, I was down to 4.5 pounds of air. That is as low as I go with my tires and only for deep snow. You may find that 6 pounds of air is very good in most circumstances. Not too high and not too low. You can’t go fast and you cannot run on hard ground or pavement at these pressures but for running on top of several feet of snow at low speeds, it is great. Those still up at 10, 15 or 20 pounds were barely able to move, for the most part, but I was able to move pretty freely. It's nothing magic. As the graphic shows, the amount of tire tread on the ground increases by about 70% or more just when dropping from 40 to 15 pounds. You can imagine how much more it changes when you drop even lower. How much you need to lower will change with snow conditions. Deep powder requires different techniques than snow-ball type snow. A bit of practice with proper techniques will get you a lot farther than most would imagine and it can be great winter fun.
There is a little more to this technique than just lowering your tire pressure so as with most things concerning serious off-roading, I highly suggest you only try this when accompanied by some experienced 4-wheelers. They can help make sure your tire and wheel combination is appropriate and that you have help should something not go as planned. Truthfully, while lowering your pressure WILL increase traction, there are a number of additional driving techniques which need to be used in conjunction to achieve the best result. Don’t forget a compressor so you can air back up before getting on the pavement. (Choosing a good compressor is a whole different write-up)