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The Best Air Pressure for Off-Roading | Inside Line

Reducing the air in your tires is by far the best (and cheapest) way to increase your 4x4's off-road performance. How low you can air down often depends on a few factors, but the benefits of dropping even a few pounds from your tires can be profound. The two biggest reasons to drop the air in your tires before you hit the trail have to do with tire conformity and ride quality. In this Inside Line breakdown, we are diving into what we’ve found works best for general trail wheeling.

While we’ll have some terrain-specific air-down articles coming very soon, we’re using this time to focus on a broader trail scenario. To demonstrate this, we’ll be using a 2018 Jeep Wrangler Unlimited Rubicon fit with a set of 37x12.50R17 Nitto Trail Grapplers. These wheels are secured by a set of 17-inch KMC beadlock wheels, which is a critical part of the air down equation as well (more on that later). While we encourage you to view this Inside Line episode on our YouTube channel, we are highlighting some critical takeaways in the article below.

Jeep wrangler unlimited Rubicon JL lift 37 nitto trail grappler off road

Tools You’ll Need

You can remove the air from your tires valve stem using anything from a pen to a key in a pinch. However, these will be painfully slow. We prefer to use a valve core remover tool to deflate our tires. This method will typically get us down from 30 psi to 7 psi in just a couple of minutes. It’s worth noting that you’ll need to be especially careful using this method as it can be easy to loose the valve core. It’s one of the reasons we always keep a few spares with us.

Also imperative to this equation is a quality air pressure gauge that can show you distinct markings for low pressure. The difference between 14 and 7 psi off-road is tremendous. For a variety of safety and performance reasons, you want to make sure you are getting the air pressure correct. We picked up this Slime gauge from our local parts store, but any low-pressure gauge will do. If you happen to leave your gauge at home, you can always refer to your vehicles TPMS (Tire Pressure Monitoring System) display if your vehicle is so equipped. They are surprisingly accurate and can serve as a make-shift pressure gauge in a pinch.

Off road tire deflator tire guage

PSI

There’s no one-size-fits-all PSI (pounds per square inch) air pressure number for every 4x4, but there are a few general rules to follow. The first is the most important. If you are NOT running a beadlock wheel, we highly recommend you AVOID dropping your tire pressure below 10 psi. Going below 10 psi without some type of locking mechanism to secure the bead of the tire to the wheel can cause the tire to de-bead. This will leave you changing out your tire on the trail and with a potentially damaged tire and/or wheel.

We recommend starting at 20 PSI and working your way down from there. The weight of the vehicle, size of the wheel, tire diameter, and even the terrain you are on will all be factors. In our experience with both the JK and JL Jeep Wrangler platforms on 35- and 37-inch-tall tires, we typically will lower the tires between 10-12 PSI on a non-beadlock wheel and 5-7 PSI when equipped with a beadlock. While some sand and snow wheeling will call for even lower pressures, the aforementioned are the most common.

Jeep wrangler unlimited Rubicon JL lift 37 nitto trail grappler off road

Locking The Tire

If you see yourself regularly hitting the trail, invest in a set of beadlock wheels. Unlike a standard wheel which uses air pressure to keep the tire in place, a beadlock wheel uses some sort of mechanical mechanism to “lock” either one or both of the tire beads in place. Having the tire locked to the wheel is what makes it possible to drop into that critical single digit air pressure range off-road. With so many tires being constructed with Load Range D, E, and even F ratings, getting down into the single digits is often necessary to allow the sidewall to flex.

Jeep wrangler unlimited Rubicon JL lift 37 nitto trail grappler off road beadlock wheels

Off-Road Performance

Think of your tire for a moment as a basketball. A fully inflated basketball will bounce with ease. This is due in part to the high air pressure inside of the ball. When you have street pressure in your tires, this same bounce principle applies. Instead of conforming to the terrain, your tire is constantly pushing away from it. This equates to a harsher ride and poor off-road performance. Just like the basketball, if you let enough air out, it will stop “bouncing” and start to conform to the terrain. As you can see here, the tire is absorbing the rock rather than pushing away from it. This not only helps the tire grab the rock (hello traction), but by absorbing the rock it's creating a smoother ride.  

nitto trail grappler 5 psi off-road review

Critical Tire Choices

It’s important to note that not all tires can handle low air-pressure abuse off-road. Without question, you are putting more strain on the tread and sidewall of the tire on the trail. In places such as Uwharrie National Forest where sharp rock outcroppings are common, it’s easy to find yourself with a sliced sidewall if your tire is not built for this type of abuse. This is one of the reasons the Nitto Trail Grappler has become one of our favorite all-around tires. Since we drive, not trailer, our Jeep to the trail, having a tire that can handle serious off-road terrain is wildly important. The Trail Grappler simply has one of the toughest sidewalls of any mud-terrain radial on the market.

Jeep wrangler unlimited Rubicon JL lift 37 nitto trail grappler off road

Ride Comfort

We can’t stress just how much better your wheeling experience will be with lower air pressure in your tires. When you are spending all day on the trail, every bump that your tire can absorb is one more that you don’t. This helps with driver fatigue way more than you might realize. With many door placards calling for 35 to 45 PSI on the highway, just dropping down by 15 pounds can make a major impact over rough terrain.

Jeep wrangler unlimited Rubicon JL lift 37 nitto trail grappler off road

Airing Up

While airing down is free, airing up usually isn’t. Before we get back on the road, we break out our VIAIR compressor. We’ve been using the 400P for the past five years and found that it works great. It’s not super-fast (around four minutes per tire), but we can latch the air chuck in place and do other things while it’s airing back up. If you don’t want to spend money for an onboard air system just yet, make sure you note where the nearest pay-to-pump air compressor is to you BEFORE you air down on the trail. Driving at highway speeds with low air pressure is dangerous for you and those you are sharing the road with.

Jeep wrangler unlimited Rubicon JL lift 37 nitto trail grappler off road

Learn more Off-Road Basics by clicking here.

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