Viair 400 Compressor

Let’s Talk Viair Compressors – The 400p

The concern that you will be out on the trail at some point and get a flat tire is not unfounded. It’s like owning a motorcycle. If you have one for any length of time, the chances that you kiss the pavement lend validity to the common theme of “when”, not “if”. Keeping a properly-inflated spare tire is important, as that’s a fairly easy swap depending on the terrain. But that’s a one-time-per-outing fix; if you lose another tire… well let’s hope you’re with friends.

A great solution to this problem is to carry a portable air compressor and a patch kit. With a decent air compressor you can re-inflate a tire, re-seat a tire bead, or even run air tools or a blender- you know, for when you’ve accomplished a tire fix on your own and you have extra ice for a cold drink.

There are several well-known air compressors out there that fit the bill. Some are very inexpensive and lightweight, while others can cost upwards of a thousand bucks and will run without overheating, come in a military-grade box that floats, and an air tank to help with a steady supply of high-pressure air. Most people will stick to the best value however; the tool that does the job, can stand up to years of use, and is relatively inexpensive.

The Viair 400p 12-volt air compressor is a fantastic value. Read on to find out why I have one in my truck.

Viair 400p Basic Kit

What’s in the Box

The Viair 400p comes in a couple of varieties. The less expensive version gets the compressor, extra filters, fittings, 30 ft coil hose, and a sturdy canvas carrying bag. If you opt for the Viair 400p-a, you’ll get an air gun in place of the simple locking chuck.

Viair 400p-a with air gun

The advantage here is that the large pressure gauge is on the gun, and gives you the current pressure when you let off the trigger. This option is a bit more expensive though.


The Viair 400p air compressor base stats include 150 psi max pressure and up to 2.30 cfm. At 30 psi it still retains a respectable 1.86 cfm. This means that inflating a 35″ tire from 15 psi to 30 takes about 2 minutes 45 seconds, which is better than most. Viair claims a 33% duty cycle. That’s not as good a some, but it’s a long cycle, up to 40 minutes before it needs to cool. That’s plenty of time to air up a full set of tires or two when you’re leaving the trail.

Viair 400 Compressor

Some nice upgraded features that you won’t find in less expensive varieties have been included. Auto-shutoff serves two functions. First, the compressor will stop running when it gets too hot, and then reset when it has cooled sufficiently to resume. Less expensive compressors use a reset button. The second function will stop the compressor when you disconnect to switch to another tire. This saves trips (and frustration) turning the compressor on and off every time you switch.

Standard NPT fittings come on either end of the hose, if you selected the air gun. This makes it easier to find replacements and additional accessories as compared to some other non-conventional fittings found on other compressor kits. The hose is a standard 200 psi coil hose, 30 feet long, and the power cord is 8 feet long, so between the two you can reach most RV tires.

The maximum draw on your battery is 30 amps, but it’s only using about 23 at 30 psi. That’s about in the middle of the pack. Cheaper alternatives will run at 15-20 amps, while high-end systems can pull over 50 amps.

The compressor is mounted to a diamond plate sand tray with rubber isolators to keep it on top of loose soil and mud.


Most kits come with a 30 foot, 200 psi black coil hose. If you get the air gun, the hose has npt quick-release fittings on either end. If you don’t, you get the locking chuck on one end, with a npt on the other.

The air gun is easy to hold on to, and the attached gauge is easy to read. It comes with a 12-inch rubber hose with locking chuck, and a pressure relief valve.

The 8-foot power cord includes two quality battery clamps that are easy to grip. A 40 amp fuse is included and easily accessible.

Viair compressor and Accessories

The canvas carrying bag is tougher than other light-duty nylon bags. It will resist sharp rocks and sticks, and hold up to typical abuse you’ll find off-road. There are two compartments, one for the compressor & cord, and one for the hose. The compartments are large enough to easily zip closed with everything inside, but not so large as to take up unnecessary room.

Using the System

Using the compressor is straight forward. Pop the hood, place the compressor on the ground next to the engine and connect the power leads to your battery terminals. Uncap the tire valve stem, clamp on the hose and flip the switch.

If you’re airing up after a day on the trail, make sure you know how much pressure you need to run safely on the highway (for my heavy truck I run a minimum of 50 front and 60 rear). If you can go with less than 40 psi, the auto shutoff will kick in when you’re ready to switch tires. Any more than that and you should probably flip the power switch on the compressor, depending on conditions such as outside temperature.

Great Product for Most People

If you are the kind of driver that occasionally goes off-road, or if you a serious off-roader, this is a fantastic compressor. It is reasonably compact and can tuck into a corner of your rig. It’s great for airing up a volleyball at your campsite, or re-seating a tire if you pop a bead on the rocks. It will handle a set of 4 tires without a hiccup, and maybe a friend’s as well before you need to let it cool.

I remember walking into a Walmart a few years back and I saw a guy standing next to his little motor home with a mini compressor buzzing away, trying to fill a tire. It was a small one, the $30 kind that plugs into a cigarette lighter. Twenty minutes later I came out and that thing was still buzzing away, still attached to the same, near-flat tire. I asked him if he was making any progress and he didn’t seem to want to talk about it. That experience helped me decide to get a new compressor.

What I Like

  • Auto-shutoff with thermal protection
  • Sand tray
  • Air gun
  • 30 foot hose
  • Short air-up times
  • Standard NPT fittings

What I Don’t Like

  • 33% Duty cycle
  • Made in China

Final Thoughts

If you have a lot of work to do with the compressor, such as lining up several rigs, or running air tools at a site, you will want to look into adding an air tank or a more powerful compressor, or both. If you are going to stay on the pavement and just run stock tires, you don’t need a compressor in this range.

For everyone else, I’d recommend this kit. It comes with a lot of useful features such as the auto-shutoff, it will run long enough on a cycle to complete most jobs, and it is durable enough to last for years.

If you have any questions about this compressor or anything related, or if you have experience with it, just drop a comment below for some good discussion.

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