How to Choose the Best Air Compressor for Off-Roading

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Words by Chris Emery

A quality air compressor is perhaps the most important purchase every new off-road enthusiast needs to make. Not only are they essential for inflating tires after airing down or fixing flats but - depending on the model - they can be used for differential lockers and even powering air tools. 

Like a lot of aftermarket gear, the choices of air compressors can get overwhelming when trying to determine the best one for your applications and 4x4. From the styles of models available to technical components, listed below are the essential details about the types of air compressors for off-roading and the basics to consider before purchasing one.

What are Air Compressors Used For?

There are two main tire-related uses for air compressors when off-roading. The most common use comes after you deflate tires to improve traction, prevent tire damage, and soften the ride on the trails. In this case, you use the air compressor to reinflate the tires when leaving the trail for the pavement or to adjust the pressure mid-trail to adapt to changing terrain. The other primary use is for reinflating a tire after a repair, reseating a tire or adding more pressure to a spare. 

Types of Off-Road Air Compressors

A couple of air compressors are available, onboard and portable. A third option, which is popular among offroad competitors and hardcore wheelers, is portable C02 or nitrogen tanks that have rapid inflation rates since the gas expands quickly once it’s in the tire.

Onboard Air Compressors

Onboard air compressors are commonly mounted in the engine bay (or another convenient and concealed area elsewhere on your vehicle) and wired to the battery. While this is convenient since they are always connected to a power source and ready to run at a moment’s notice, they can often serve multiple purposes as well. They can power the pneumatic control for air-lockers on differentials while larger units can power air tools such as air impact wrenches to quickly remove wheel lugs.

Typically, when an onboard system is installed, switches are integrated into your 4x4’s dash or somewhere else on the vehicle so the differentials can be locked from inside the cab - no more climbing out and twisting the hub on the wheels.

  • Pros: Convenience on the trail; multiple uses include powering air lockers and tools.
  • Cons: High cost of initial installation; difficulty accommodating some engine bays without modifications; upgrades and repairs to the compressor are more costly/time-consuming.

Portable Off-Road Air Compressors

Portable off-road compressors are transported in a bag or case and connect to the battery terminals when needed. More compact models simply plug into 12V ports, but keep in mind these may not be powerful enough for tires of trucks or other 4x4’s. But some of the more powerful units offer more flexibility than onboard systems and are great choices. 

For example, they can easily be used on other vehicles and conveniently reach tire valves (depending on the length of the battery clip wires on some models) without over-stretching the air hose. Remember, every time it’s needed, it has to be unpacked, connected to the battery, and then cool down before being repacked. This can be a little bit of a hassle and eat into some of your run time on the trails.

  • Pros: Relatively inexpensive; no installation required; the flexibility to easily move the unit.
  • Cons: Hassle to unpack, use and repack; takes up room inside the vehicle.

Portable CO2 and Nitrogen Tanks

Portable tanks filled with carbon dioxide or nitrogen resemble scuba diving tanks (yet are smaller) and offer rapid inflation as these gases are compressed more than oxygen in the tank, and then expand quickly when blown into a tire. If you go wheeling quite a lot or have large tires that can take a long time to inflate, these can save a lot of time. However, the amount of CO² and nitrogen in the tank is finite so you’ll want to bring along a compressor as a backup.

  • Pros: Rapid tire inflation on the trail; fill large tires more easily.
  • Cons: High cost due to the need for another air compressor; a finite number of tire inflations; the tanks need to be refilled and take up space and add weight

OnBoard or Portable?

Whether you choose an onboard or portable air compressor may come down to whether you have air lockers on your axle differential.  If you do, it’s probably worth the cost and added convenience of an onboard unit. In our opinion, if you don’t have air lockers, a portable compressor is a more flexible and cheaper option than the cost and time of installing an onboard model.

How Large are Your Tires?

The volume required to inflate your tires will greatly determine your choice. You’ll be bored to death waiting for an underpowered air compressor to inflate 33” or 35” (or larger) tires. Plus, if you exceed the duty-cycle rating before the inflation is complete, you’ll have to wait to let the engine of the air compressor cool down before inflating all of the tires. 

Manufacturers commonly offer guidance on which of their models are practical for different sizes of tires. Compressors ideal for larger truck or Jeep tires typically connect directly to battery terminals as 12V outlets don’t have enough amperage. 

But How Patient are You?

More powerful compressors push more volumes of air per minute, hence they inflate tires more quickly. So, the faster you want to air up, the more powerful the air compressor you should get. If you want to speed up the process more, consider a CO² or nitrogen tank system.

Choosing Manufacturers

A number of companies make portable air compressors for trail running and overlanding. At the high-end, ARB manufactures both onboard and portable units and are considered the gold standard, yet they come at a cost. VIAIR also makes a variety of units and are solid systems for reasonable cost and value. For further cost savings, Smittybilt offers portable air compressor models if you have a tight budget. Remember, you do get what you pay for and in the event you’re not putting your compressor under heavy use, the latter might be the better option for your application(s).

Does it Have a Deflation Mechanism?

Airing down your tires can also take time. Fortunately, some air compressor valve chucks come with built-in mechanisms that can release pressure from the tire without having to depress the valve stem. This is a feature worth having. Some tire gauges also come with this feature. We own a set of auto-deflators that can deflate all of our tires at once, which is recommended if you do a lot of off-roading.

Air compressors are one of the first items to purchase for any type of off-roading as airing down your tires on rough terrain has many benefits and you’ll always need a way to inflate them. While you can find a compressor that is capable of filling your tires slowly, we suggest purchasing a unit that’s more powerful to save time should you upgrade to larger tires in the future or wish to power other systems. Either way, an air compressor is a great investment and a tool that you will use for as long as you run the trails. 

About the author: Chris Emery is the editor of Ordealist.com, a website dedicated to overlanding, off-roading and vehicle-based adventure. 

Understanding Parts of Off-Road Air Compressors

Here’s an overview of the various parts of an air compressor. We’ve included some of the ratings such as pressure, duty cycle, and airflow to determine which unit is ideal for your vehicle and your needs.

Motor

Reciprocating air compressors, the type used in off-roading, has a motor that powers the piston in the compression mechanism.

Compression Mechanism

The compression mechanism consists of a valve that allows air to be drawn into a cylinder. A piston then forces that air through the air hose and into the tire. This cycle repeats until the tire is inflated.

Air Hose

The air hose carries air from the compressor to the tire. Remember, it’s important to have a long enough hose to easily reach all tires when connected to the battery or 12V outlet.

Tire Chuck

The tire chuck is the part of the compressor that connects to the valve stem. For compressors used in off-roading, it’s recommended that the chuck has a built-in deflator and inline pressure gauge.

Power Cord/Wiring

The power cord or wiring (in the case of an onboard model) connects the compressor to a power source, whether it’s directly connected to the vehicle’s battery or through a 12V outlet.

Air Compressor Ratings

Compressors used for off-roading are typically rated according to the following parameters:

  • Tire Size: Some manufactures indicate what air compressor is ideal for a given tire size. Typically, this comes down to the compressor’s airflow capacity (measured as CFM), which is explained below.
  • Pounds Per Square Inch (PSI): This is the force of air that the compressor delivers. The PSI is particularly important for running air tools, and most off-road air compressors deliver plenty of pressure to inflate truck and 4x4 tires.
  • Cubic Feet per Minute (CFM): CFM indicates the air volume the compressor can supply per minute. This tells you how fast a compressor can inflate a tire. Run time depends on the duty cycle (see below) and having a high CFM is essential for inflating large truck tires (and can also speed up the inflation of any tire). If you have the budget, it’s worth it in time savings to choose a compressor with a high CFM versus one with a lower CFM.
  • Duty Cycle: As compressors alternate on/off cycles to prevent overheating, the duty cycle is the ratio of on-to-off time required during a one-hour cycle. For instance, a compressor with a 50 percent duty cycle can run for 30 minutes during one hour. In hot conditions, the cool-down time will increase as the compressor will heat up faster. If you purchase an air compressor that is not powerful enough for your tires, you won’t be able to fill them all without letting it cool down. 
  • Voltage: Air compressors used in off-roading are typically 12 or 24-volt models. Larger compressors require higher voltage and deliver higher airflow and pressure.

For inflating tires for off-roading, a tire size rating is the handiest measure for deciding what compressor to buy. If a straightforward tire-size guide isn’t available, use the other ratings to choose the right unit for your needs.