SEE THE PHOTO FOR A REPRESENTATION OF THE DIFFERENCE AIRING DOWN MAKES TO YOUR TIRES AND TRACTION PATCH: (Result may vary)
Airing down (DEEP Snow Edition)
This particular post has nothing to do with normal driving tire pressures. This primer is about short, off-road (off-pavement) driving in deep snow where increased traction and floatation can be helpful. It is NOT about driving down the interstate in your smart car (or anything else). NEVER ATTEMPT SUCH LOW PRESSURES WHEN ON PAVEMENT OR OTHER HARD SURFACES OR AT SPEEDS ABOVE A FEW MPH!!
A quote from the Discount Tire website: “Airing down your off-roader’s tires simply means deflating them across varying levels of air pressure/PSI. By reducing the air pressure in your tires, it increases the surface grip on any rocky trail. In fact, many all-terrain and mud-terrain tires are designed to be aired down.”
Now that we have that out of the way:
We air down in the summer to increase our traction on loose dirt and rocks and to smooth out the rough and bumpy trails. We often air down to around 15 pounds for these summer and light snow conditions. It varies with different tires and/or vehicles. (We have a separate write-up for that) However, we may air down considerably more for winter trail rides in DEEP SNOW. OK...a LOT more.
On a winter trail ride, last year, we had many people who were new to deep snow-wheeling joining us. We were wheeling, in the mountains, in 2-3-5 feet or more of snow. It was not a ride to the mall. On this trip, we were climbing steep hills, and those still at 10, 15, or 20 pounds (or even more) could barely move and were often stuck. Those who aired down correctly for the snow could move pretty freely. Once we showed the others how to do this, they ALL did much better.
Most often, a significant challenge is getting people to lower their tire pressure enough to gain the needed traction and floatation. Cutting through snow may be acceptable when in a foot of snow, but several feet of snow and you sinking into the snow becomes a real problem. This technique is excellent for “packable” (think: good snowball-type) snow, as it may allow you to "float", or at least not sink as much. It is not as effective, though still far better than full air pressure, in powder snow.
Let’s face it; we have all heard that having your tire pressure below 30 pounds(or some such) will result in a tire catastrophe. Yet here you are being told to lower your pressure considerably below 30 pounds. While not entirely accurate across the board, they are speaking of ON-PAVEMENT driving at normal road speeds, not off-roading at five mph.
While bead locks are great, only some rigs in my wheeling groups have them. Beadlocks will allow you to go to even lower pressures without risking bead loss, but you can utilize this technique with many non-beadlock wheels.
Some combinations of tires and wheels are better than others, so your results may vary. Of course, I am not talking about running these ultra-low pressures on paved roads or at normal road speeds. I am only talking about driving deep snow-covered trails. 10 to 15 mph is at the VERY TOP of the speed scale. This is about driving in DEEP snow, while in 4-low, and usually in 1st gear...it is unlikely you can get to 10mph most of the time. You cannot drive the same way you would with normal pressures. The rule is, “the lower you go, the slower you go.”
On this trip, I eventually aired down to 4.5 pounds. That is as low as I go with my current tires and then only for DEEP snow. Some people should not go that low, but others may be able to go lower. There is no magic pressure that is right for everyone. Some, with 35” tires (for example), may find that 6 to 8 pounds of air can work well in many circumstances. Not too high and not too low. You shouldn’t go fast and cannot run on hard ground or pavement at these low pressures, but this is excellent for running on top of several feet of snow at low speeds.
It’s nothing magic. As the simple illustration shows, the contact patch of tread on the ground can potentially increase by 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 lower pressures may change with snow conditions. Powder snow requires different techniques than snow-ball (packable) type snow. A bit of practice with proper techniques will get you much 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. Hence, as with most things concerning serious off-roading, I suggest you only try this when accompanied by some experienced 4-wheelers familiar with doing this. They can help ensure your tire and wheel combination is appropriate and that you have help should something not go as planned. While lowering your pressure CAN increase traction, several additional driving techniques must be used to achieve the best result. At least one locker (preferably two), 4-Low and low gearing are best. Don’t forget an air-up device (compressor, co2-tank, etc.) so you can air back up before getting back on the pavement.
This is serious off-roading. As always, we highly recommend you do not try or do this alone. This is about DEEP snow; just like with deep mud, you will get stuck sooner or later. That is just part of snow-wheeling.
As a parting shot: Many people feel a need to point out that this technique can cause additional wear to your tires and other vehicle components, that it lowers MPG, and that you may get stuck doing this. In response, I say...so? As a general statement, off-roading WILL wear out some components faster or add the potential of trail damage. Climbing over large rocks and trees, crossing rivers and streams, and driving in mud or sand WILL, of course, use more fuel and have more potential for wear and damage than normal driving on the freeway. That is something you must accept to participate in this hobby. If you are averse to that, off-roading may not be for you. Off-roading really is not for everyone and staying in the mall parking lot is absolutely safer.
Disclaimer: The graphic is not intended to be an exact representation of what happens with every tire, tire model, tire load rating, or every tire/wheel combination, when aired down. It is just a visual representation for general reference.