If you have been reading 4WOR for long you have likely heard us extol the virtues of airing down your tires on the trail for increased traction and an improved ride. Airing down can be as easy as holding down the valve core with a car key. Airing back up, however, is a little more complicated. You don’t want to drive on the pavement at high speeds with deflated tires. The extra rolling resistance creates heat in the tire’s carcass, which can cause them to delaminate and fail.
Enter Viair, which offers a whole host of air compressor options to fit any budget and application. Our 2002 Tundra shown here had a huge amount of free space under the hood, so we ordered up Viair’s Ultra Duty Onboard Air System and hard-mounted the 480C compressor in the engine bay and the 2 1/2-gallon air tank inside the framerail. Dual compressors and even portable units are also available from Viair if those better suit your needs. Onboard air is useful not only for airing up your tires but also for operating air lockers, running air horns (if that is your thing, hopefully it isn’t), inflating air mattresses, and even blowing out the interior of your rig after a dusty day on the trail.
What to Look For in an Air Compressor
There are a variety of factors to consider when shopping for an air compressor. Do you want a hard-mounted or portable compressor? How much are you looking to spend? Do you plan to air up tires, fill airbags, or run air lockers? Perhaps the two most important factors are airflow (cubic feet per minute, or cfm) and duty cycle. A higher cfm rate means the compressor moves more air, but note what pressure that airflow is at. A compressor made to inflate an air mattress might move a lot of air, but not at the pressure necessary to fill a tire. Duty cycle is the length of time an a compressor can run in an hour before needing to cool down for the remainder of the hour.
Viair offers individual compressors as well as air systems, such as the Ultra Duty system shown here. This comes with everything you need from the compressor and tank to the fittings and wiring, allowing you to perform a complete installation without having to track down all of the little parts and pieces.
Viair packages the components for the installation into four separate bags, which are labelled. One bag contains the parts for the air tank installation, like compression fittings. The second bag has parts for the compressor install, such as electrical connectors. The third bag has the pressure switch and reducer. The fourth bag contains the parts for the gauge installation.
Not all compressors are created equal. Viair’s 480C compressor has 100 percent duty cycle at 100 psi and can fill a 35-inch-tall tire from 15 psi to 30 psi in three minutes 15 seconds. It features horizontal cooling fins and a trapezoidal head design with a standard 3/8-inch stainless steel braided hose.
We had a large space to work with under the hood of our 2002 Toyota Tundra, making for an easy installation. Bradd Davidson from B-Radd Customs handled the installation in a day, including making some custom brackets under the hood.
We found the included fittings a challenge to install of the air line from the compressor to the pressure switch and tank. The plastic line was difficult to straighten out after being coiled in the box as well, but some heat solved both issues and we haven’t experienced any leaks.
The battery in our Tundra is located on the driver side of the engine bay, and we mounted the Viair compressor on the passenger fender, but the included wiring was long enough to cleanly route in front of the radiator along the core support. Viair includes an inline fuse and ring terminals to make the wiring a breeze.
Air tanks aren’t particularly useful for airing up tires since the tank empties before the first tire is even at street pressure. They can be useful though for items like air lockers or air tools, where you need a quick blast of high-pressure air. We mounted our tank inside the framerail next to the exhaust, with the safety valve mounted up and the petcock pointed down to drain any condensation.
The Viair Ultra Duty Onboard Air System comes complete with a pressure switch and a relay that will turn the compressor on at 110 psi and off at 145 psi. The pressure switch has a 1/8-inch NPT inlet at the bottom to allow it to be plumbed directly to the air tank.
Bradd Davidson made custom brackets under the hood for the air chuck and pressure switch using a vertical band saw and a sheetmetal brake. He then used existing hardware on the inner fender to cleanly mount these items.
The completed installation looks like it came from the factory. Thanks for all that space, Toyota! While the pressure gauge can be mounted in the interior and the air chuck can be positioned in the wheelwell or on the bumper, we like the stealth installation and don’t mind popping the hood when it comes time to air up the tires.
Viair includes a 30-foot coiled air hose, which was long enough to reach all four tires on our Tundra. The Ultra Duty Onboard Air System also comes with an inflation chuck that is easy to operate with gloves on and has an integrated 0-200 psi gauge.
The addition of onboard air from Viair allows us to air down our tires with the confidence of knowing that we can quickly air back up when necessary, and even remount a tire should it come off the bead. This is a huge advantage in the sand dunes, where low tire pressure can mean the difference between getting stuck or getting rad.