Viair 400P – Automatic Portable Compressor

VIAIR 400P – Automatic Portable Compressor Review

Viair 400P-Automatic Portable Air Compressor Review

Overview and Review of the Viair 400P-Automatic Portable Compressor – After roughly a year of consistent use.

If you enjoy four-wheeling and tackling new obstacles off-road, chances are you air-down your tires when hitting the trail. That off-road traction and performance enhancement, however, comes at a price once back on the tarmac.

At best, under-inflation increases the wear and tear on your tires, reducing tire lifespan, and results in relatively lower fuel economy. (Not that any of us buy our 4Runners for the MPG, but if you could preserve a little bit, why wouldn’t you want to?) And, at worst, under-inflated tires are a safety risk that can cause or contribute to accidents – especially at highway speeds.

So, once you’re done on the trail for the day, what do you do? Borrow an air supply from friends? (Maybe.) Try to remember where that last gas station was and hope they have a functioning air system and that you have enough quarters on hand for the fill? (If there isn’t another option.) Take the gamble, roll the dice and head home? (No!) Or do you carry your own air supply and up your self-sufficiency game? (A-hem, Winner!)

Decisions, Decisions, Decisions

Viair 88P - Viair 400P Compressor

Once you’ve made the (smart) decision to carry your own air supply, you will have undoubtedly noticed the myriad of options available.

Everything from complete onboard air systems (OBA’s) to portable tanks to other popular portable air compressors are available from numerous retailers at price points starting below $100 and quickly escalating to over $500.

Portable Compressor Options 

The key to deciding which solution is right for you is to understand your needs versus your wants and balancing both against your budget and the features and functionality of the options available within your budget to arrive at the best value for your situation.

Viair 400P Compressor Overview

Viair 400P Compressor Details

When it came time for me to decide, I knew my needs were pretty simple. I don’t have pneumatic tools for the trail nor lockers requiring an OBA system and I didn’t want to hassle with refilling tanks.

What I needed was a reliable way to air up my tires within a respectable amount of time that was more robust than the little cigarette lighter/110v combo unit I have in the garage for my kids’ bike tires and soccer balls. Oh, and I didn’t want to spend a fortune on it.

Having outlined my needs and wants and a budget, I explored my options and quickly settled on a portable air compressor. A little more research yielded noteworthy options from the usual suspects in the off-road product’s community, but I was intrigued by the offerings of Viair – a popular brand in this space.

They offer a wide array of options from little cigarette lighter powered compressors to high-end OBA systems and they have a variety of mid-range air compressors that were in line with what I was looking for. After some additional pondering, and a timely price break from one of my favorite online retailers, I settled on the Viair 400P-Automatic Portable Compressor.

Viair 400P Compressor Features

Viair 400P Automatic Compressor Features

A couple of key features beyond a decent price-point really sold me on Viair’s 400P-Automatic Portable Compressor.

First off, it offered reasonable performance for the price.

Viair states the 400P-Automatic has a 33% duty cycle at 100 PSI and can be operated for up to 40 minutes at a time before needing to be rested. Additionally, the automatic shut-off feature means the unit automatically shuts down when not in use, saving the user from going back and forth to do it or from having the unit continuously run even when not in use.

Additionally, the compressor came as a kit with a quick-connect 30-foot air hose; quick-connect gas station style tire inflation gun with built-in pressure gauge and pressure release valve; and a storage/carrying case to keep it all in order.

Key features, specifications, and fill rates from Viair on the 400P-Automatic are:


  • Gas Station-Style Tire Inflation Gun with 160 PSI Gauge
  • Automatic Shut-Off Function
  • Quick Connect Air Hose with Heat Shield
  • Vibration-Resistant Diamond-Plate Sand Tray
  • Deluxe Dual Compartment Carry Bag
  • 40-amp Inline Fuse Holder
  • Dual Battery Clamps
  • 3 pc. Inflation Tips Kit


  • 12-Volt
  • Permanent Magnetic Motor
  • Duty Cycle: 33% @ 100 PSI
  • 2.3CFM Free Flow @ 0 PSI
  • Max. Working Pressure: 150 PSI
  • Max. Amp Draw: 30 Amps
  • Ingress Protection Rating: IP54
  • Dimensions: 10.87″L x 5.83″W x 7.48″H
  • Net Weight: 10.70 lbs.
  • Power Cord Length: 8 ft.
  • Air Hose Length: 30 ft.


31″ X 10.5″ FILL RATE
0 to 30 PSI 3 min. 00 sec. (± 10 sec.)
15 to 30 PSI 1 min. 35 sec. (± 05 sec.)

33″ X 12.5″ FILL RATE
0 to 30 PSI 4 min. 20 sec. (± 10 sec.)
15 to 30 PSI 2 min. 05 sec. (± 05 sec.)

35″ X 12.5″ FILL RATE
0 to 30 PSI 5 min. 20 sec. (± 15 sec.)
15 to 30 PSI 2 min. 45 sec. (± 10 sec.)

Experience and Using the Viair 400P Compressor

Experience and Using the Viair 400P Compressor

My first opportunity to use the Viair 400P-Automatic Portable Compressor was last July after airing down to near single digits to get out of some snow drifts that I had gotten stuck in at the top of a ridgeline up around 8,000 ft.

Once unstuck, I was happy to have the ability to add some air back into my tires so I could head back down the trail without fear of losing a bead and then to be able to air all the way back up to ‘normal’ to head home. I would not have wanted to drive my 4Runner on the highway at the low tire pressure I ended up needing to get unstuck.

After just about a year of ownership and several more uses since last July, the Viair 400P-Automatic Portable Compressor has met expectations and I have been happy with its performance.

Although I haven’t scientifically tested it, my sense is that the fill rates listed by Viair are reasonably accurate and the fill times are generally consistent with my experience. The air gun with gauge makes airing up to the desired pressure a breeze and the 30 ft. hose puts each corner within easy reach. The power cord is a decent length, the alligator clips hold to the battery posts tight, and the whole kit stores neatly in the carrying bag.

While I do not have any significant concerns with the 400P-Automatic Portable Compressor, the user experience would be improved if the alligator clips opened a few millimeters wider to get them over larger battery posts. And during a particularly hot day last summer, I did overheat the air hose causing one end to slip off its quick-connection. (Although it was easily repaired with a $1 hose clamp.)

Final Thoughts

Airing down your tires is an easy, free ‘mod’ that you can do to improve your 4Runners off-road performance. Getting (and keeping) your tires aired up is necessary maintenance for safe and efficient highway use.

The 400P-Automatic Portable Compressor from Viair is a great accessory to add to your kit to make that maintenance item a bit easier to knock off your list.

Its made my off-roading experience better and it is easily one of my most often used accessories. If you’re in need of a portable air solution, the 400P-Automatic is worth consideration.

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2 years ago

What kind of inverter is needed if you want to use this out of your garage once in-a-while? In other words, has anybody used an AC-DC inverter to use this compressor from shore power?

James Cooper
James Cooper
2 years ago

Thanks for this review. Torn between this and the ARB portable options. The price of this makes more sense for my occasional use forecast.

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