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 builtin 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.