If you've ever been on a Jeep run with others, you probably saw everyone messing around with with their tires and front suspension right before heading out on the dirt. No, they are not doing a last minute check on their Jeeps. Well, they might be doing that too, but more likely they are letting air out of their tires and disconnecting the anti-sway bars from their front axles. This is a ritual almost everyone does before heading out on a trail. So why do they do this? I am glad you asked.
Letting air out of the tires, or airing-down as it's called, is the process of lowing the air pressure in your tires. When driving around on paved streets, the ideal air pressure in your tires is much higher than the ideal air pressure that you would have when going off-road. Typically the air pressure in your tires is probably around 30 to 40 psi (pounds per square inch). This will vary with your manufacturer's recommendations and the type of tires you have. The high pressure is what makes your daily drive on pavement possible. It allows your Jeep drive fast on the freeway and also helps the sidewall of the tire stay rigid while making sharp turns. However these helpful features of high pressure aren't necessarily what you want when driving off road over rocks and sand.
When driving over rough terrain with high tire pressure that you would use on pavement, you will tend to feel every rock and pebble that you drive over. By airing down your tires, the tread will tend to absorb the bumps better because the tread can deform slightly over the rocks and bumps. Imagine two basket balls, one is inflated to its normal pressure, and the other is deflated. If you bounce the inflated ball, it will bounce back. Try to bounce the deflated basketball, and it will just fall flat. The same principle applies to your tires. Normally inflated tires will tend to bounce off of every bump and rock, while an air-down tire will smoothly roll over the bumps, providing a much better driving experience.An aired down tire showing how the tread contours over rocks
A second benefit of airing down your tires while offroading is that your tire tread will deform to whatever surface it is on. This allows more surface of the tread to touch the rock your are driving over, providing a better grip on the rock. This is helpful when "rock crawling". You would be surprised how much better an aired down tire performs on rocky surfaces than a fully inflated tire. Also along with the concept of more surface area of the tread touching the ground, you will see significant improvement while driving through sandy terrain.
So how much air should you let out of your tire when offroading? You don't want to let so much air out that your tire is flat. That will ruin the tire and possibly make it come off the wheel. Personally, I air my tires down to about 8 to 10 psi when on the trail. Some Jeepers will take it a little lower, some a little higher. You will need to experiment with your tires and type of terrain you are diving on to get the perfect tire pressure. Going too low may result in the tire popping off the wheel. And not airing down enough will do nothing and will defeat the purpose of airing down in the first place.
How do you let the air out of your tires? There are many after market tools available to assist with quickly getting all that air out. I use a Currie E-Z Tire Deflator to air down my tires. This is a relatively inexpensive tool that does a great job of quickly deflating tires. Basically it just attaches to the valve stem on the tire, and with a few twists, air is rushing out. It has a built in gauge so you can see your tire pressure in the process, and stop it when it is at the desired pressure. There are other tools available too, take a look on Amazon and see what's out there. You can also just use the tip of a screw driver or similar small object to release the air out of your tires if you don't wish to purcahse a tool designed to deflate the tire. However this will generally take much longer than with a tire deflator.Currie E-Z Tire Deflator - Best Tire Deflator Available
Once you have aired down your tires, enjoy a smother ride and be amazed at how well your Jeep can handle those obstacles. This simple technique will do wonders for your off road experience.
One important step in the air-down process is the air-up process. When you are done with your trail and before you go back on the pavement, it is essential that you fill your tires back up with air. Driving on pavement at higher speeds with aired-down tires is dangerous and can cause the tire to be destroyed. This of course would be catastrophic for both your passengers, and others on the road. You should use a portable air compressor or similar to air your tires back up to the proper pressure your manufacturer recommends for street driving. I will be covering different types of air compressors and other ways of airing up your tires in a future post, so stay tuned for that.