Pressure situations happen to all of us in many aspects of our lives. Most of the time, too much pressure can lead to serious problems…at work, at home, at school…even in your tires! Let’s take a few minutes in this issue’s column to talk about correct tire pressure. Some folks barely give it a second thought but for anyone exploring the backcountry or doing some heavy hauling, tire pressure is a critical part of safe and successful travel.
One of the first things we do at Iron Range Offroad classes (right after talking about the ground rules of safety and environmental responsibility) is air down the tires. We do this to allow the tire to work more effectively over the trail. The wider footprint distributes the weight of the rig over a greater surface area (minimizing trail impact). The flex of the sidewall allows the tire to “conform” to the obstacles and grab onto rocks or stumps, and the flex of the tread allows it to dig into mud or dirt. Airing down can make an amazing difference in how much traction the tire is able to provide, and how easily you are able to manage the terrain.
How much you air down depends on a number of factors. Different types of tires (radial vs. bias ply, all terrain vs. mud terrain, stock size vs. oversize), different type of wheels (steel vs. aluminum, beadlocked vs. non-beadlocked), and even expected terrain might affect your decision how much to air down.
On one of my first 4 wheeling adventures (in the Black Hills of South Dakota many years ago) I was third in line of a pretty big group of Jeeps. As we started to climb a pretty steep hill of loose “scrabble”, I found myself spinning and sliding sideways. Before I could get into serious trouble, I backed down and lined up for another attempt. The group gathered to watch. I made it about as far on the second attempt and spun my tires into the hill. At this point one of the ol’ timers (chewing on a blade of grass) asked if I aired down. “Sure did,” I replied. I had dropped from 35 psi all the way down to 27psi. My third attempt was equally futile, and the ol’ timer repeated that he thought I had too much air. I got out of the way to let the other Jeeps pass while I aired down some more…at his recommendation down below 15psi. My tires looked almost flat, with the sidewalls bulging out and certainly didn’t feel like anything I was used to driving on.