Airing down a Sprinter

Off-Roading 101

Airing down (Summer edition)

HINT: It is not just for snow

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."

If you have spent any time around off-roaders or even web or Facebook groups dedicated to off-roading, you have heard people speaking of airing down. There is a good reason for that. Many people think it is about traction, but there are MANY benefits to airing down when off-roading. , that is just one of them.

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.

Beadlocks have their place but are not required for the pressures and low-speed wheeling I am speaking of here. I am discussing using standard, everyday wheels and proper off-road capable tires. Some wheel/tire combinations will do better than others, though.

For instance, wide-for-tire wheels are likelier to have the tires come off the bead at lower pressures than slightly thin-for-tire wheels. For example, with a 35x12.50x** tire, a 9” wide wheel may give excellent bead retention at relatively low pressures, but a 10” wide wheel may not offer near the same performance and may require higher air pressures to maintain bead retention. Generally, I have found that slightly thin (for tire size) wheels do much better than wider ones.

We are not talking about running these lower pressures on paved roads or at normal on-pavement speeds. This is ONLY about off-pavement driving at slow speeds. Caution and common sense are ALWAYS appropriate. I can only share my experience. YOU have to make the final call on the correct pressure for you and your rig.

Lower air pressures, when off-road, aid with traction by creating a larger contact patch of tread on the ground and allowing the tire to form to the road/rock surface. This additional traction is what most people think of when discussing the benefits of lowering tire air pressures. However, benefits include less vibration, less shock from rocks, and a much-improved ride overall.

Many technical trails are covered in baseball-sized to basketball-sized rocks. While not recommended for a Sprinter van. You might find yourself needing to get around an obstacle like this. At normal tire pressures, these roads are rough (really rough!) and will pretty much beat the crud out of you, your passengers, and your vehicle. A suspension soft enough to smooth these roads out would be useless at on-road speeds. However, by airing down, we help the suspension by making the tires and the resulting ride softer. The aired-down tires absorb a lot of the trail’s impacts, vibration, and roughness, making the ride much more tolerable.

An added benefit of airing down is it can be easier on the environment. That is why “TreadLightly!” recommends doing it too. The increased traction from airing down lowers the tendency of your tires to spin. Spinning tires tend to dig holes and damage the trails. Additionally, the larger footprint of an aired-down tire spreads the load (weight of our vehicle) out over a greater surface area. This helps keep us from sinking or digging into the road/trail surface as much and helps us tread lightly without making ruts.

What pressure you air down to will depend on your vehicle weight, tire size and design, and wheel design and size. Smaller tires will require more air pressure than larger tires to remain stable and carry the same load. Air pressures of, for example, 10 PSI, might be fine off-road for a 37” tire but could be far too low for a 28” tire, even in the same conditions and on the same vehicle. You may need to play with your pressures to find the best one for your vehicle’s tires, wheels, and trail conditions.

I can’t tell you what pressure you should run for your particular combination of components. However, I can tell you what I do personally. I am running E-rated, 315/75R17” tires and a 9” wide wheel under a VS30 2500 4x4. For summer trails, I am generally going to be at about 20 psi for most trails. If the trail has some higher-speed sections, I may go a few pounds higher for stability and bead security. On the other hand, if it is a particularly bumpy, slow driving trail, I might go a couple of pounds lighter, just for extra comfort.

Always remember; the lower you go, the slower you go.

A quality air-down tool will help make airing down faster and easier. But don’t forget a way to air back up. A compressor or CO2 tank is a must for airing back up to normal pressures before driving on paved roads.

Be careful out there, and always -- Wheel Safe!!

A small 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.

(shared graphic by Paul Si,.)