Viair 400P Portable Air Compressor Review

For the past few years, I’ve used the Viair 400P Portable Air Compressor for airing up the tires on my Jeep Wrangler while off-roading and overlanding. At first, I was using the compressor for 31-inch tires and later for 35-inch tires that I put on after installing a suspension lift.

Air compressors are an essential piece of equipment for off-roading and overlanding, allowing you to reinflate your tires when leaving the trail for the pavement or adjusting your pressure mid-trail to adapt to changing terrain. They can also air up a tire you’ve repaired a tire on the trail–for instance, when you’ve damaged two tires and you’ve only got one spare.

In my experience, Viair 400P is a solid choice for an air compressor for vehicle-based adventure. It’s relatively affordable, reliable, and has enough power to fairly quickly inflate off-road tires up to 35 inches. If you have tires larger than 35 inches, you’ll want to consider a larger portable compressor, such as the Viair 440P.

We’ll share more thoughts on the 400P below. In case you are just looking for a quick link to purchase it, here’s a link:

Viair 400P-Automatic Compressor

• 2.3 CFM inflation rate

• Great value

• Respected company

Viair 400P Highlights

There are a few things that stand out about the Viair 400P for off-roading and overlanding, including the compressor’s airflow rate, portability, and cost. 

High Flow Rate

Probably the most important factor is the high airflow rate of 2.3 cubic feet per minute (CFM) when using 12-volt power. The compressor also comes in a 24-volt version for vehicles that have more powerful electric output.

CPM tells you how fast a compressor can inflate a tire while running – with run time depending on the duty cycle (see below). 

Having a high enough CFM is really important for inflating large truck tires, and high-CFM compressors will speed up tire inflation. If you have the budget, it’s worth getting a compressor with a higher CFM vs. a lower CFM, just for the time savings.

At 2.3 CFM, the Viair 400P can inflate a 35-inch tire from 0 to 30 PSI in 6 minutes. Here is more detail on the fill rate for various tire sizes using 12v and 24v power:

12 Volt 400P Compressor

24 Volt 400P Compressor

Portable

The Viair 400P is a portable air compressor that can be moved between vehicles. Because it’s not tied to a specific vehicle, unlike an onboard air compressor, you can easily lend it to a friend or bring it with you if you get a new vehicle.

That said, each time you use a portable air compressor unit, you have to unpack it, connect it to the battery, let it cool down, and then pack it back up. It’s more hassle and eats into trail time, but in my opinion, it’s worth the flexibility offered by a portable compressor.

Duty Cycle

Air compressors alternate on/off cycles to give the engine a break and prevent overheating. The ratio of on-to-off time required during a 1-hour cycle is the duty cycle rating. The Viair 400P has a 33% duty cycle, meaning it can run for around 20 minutes before needing a 40-minute break. This gives you enough working time to reinflate a set of four larger tires up to 35 inches before needing to rest the compressor. 

Cost

Viair’s compressors are generally middle of the pack in terms of cost — for instance, more expensive than a Smittybilt but less costly than premium ARB models. The 400P costs around $200 as I write this, which is a good value in my opinion.

Viair 400P Features

The VIAIR 400P comes with a zippered carry bag made of a sturdy Cordura-like fabric with storage compartments. It’s a durable bag with a convenient handle on top. I let the compressor cool down before putting it back in the bag after use to avoid melting the fabric. 

The plastic slinky-like air hose is 25 feet long and comes with a 120 PSI pressure gauge and an automatic mechanism on the chock for hands-free deflation. I drive a 4-door Jeep Wrangler and haven’t had any problems getting the hose to stretch to the rear tires.

I haven’t tested out the maximum available stretch on the hose, but I typically have some slack left when I use it on the Jeep and I’m guessing it would stretch to the rear tires of most vehicles, even longer pickups and vans. 

The battery cable is 8 feet long and connects directly to a vehicle’s battery with heavy-duty clips. It's pretty straightforward. I typically move the air compressor from one side of the car to the other when inflating the tires, and I’m careful not to let the power cable rest on a hot portion of the motor to avoid melting the outer plastic sheath.

Conclusion

Overall, the Viair 400P is one of the best off-road air compressors you can get for the money. There are higher-end choices — ARBs come to mind — but this model has worked well for me for several years of regular off-roading and overlanding excursions. 

One nice thing about this model is that you can use it to inflate tires up to 35 inches. So if you are just getting started overlanding or off-roading, the compressor can grow with you as you make upgrades to your vehicle. If you get ambitious and move to tires over 35 inches, you’ll need to upgrade to a more powerful model.

Check out our guide to choosing an off-road air compressor for more information on compressors and recommendations for other models.

Some links on the site will take you to online retailers such as Amazon.com, and when you make a purchase we may receive a percentage.