OB Approved CO2 vs. Air Compressors

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4xFar Adventures

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There area variety of reasons to upgrade to an OBA (On Board Air) setup in your rig. Maybe you've purchased bigger tires and the little $30 compressor from the auto parts store won't cut it any more. There's the option of running air tools, though that may also require an air tank.

You're options are basically a CO2 setup or an air compressor. Each has their pros and cons. It's up to you to ultimately decide what will work best, based on your needs.


CO2

CO2 is liquefied carbon-dioxide, typically stored in a 10# or 20# tank. Power Tank is the standout (and most $$$) manufacturer of tanks and accessories. Their yellow powder coated tanks are well known, and seen among the 4WD community.

These tanks need to be stored upright and hard mounted inside your rig. For ease of access to the tank for refilling, there is usually a metal strap that unlatches and the tank can be pulled out. This must be accounted for when picking a mounting location. For example, my CO2 tank is only 4" away from the ARB fridge. Without the fridge slide, there would not be enough room to fully open the latch straps and then remove the tank.

When it comes to filling tires, the speed at which CO2 performs this task is second to none. It's extremely fast, and can produce a large volume at the same time. This is important if you want to re-seat the bead of a tire. Using a large ratchet strap around the tread of the tire will direct the expansion to the sidewall, and seat the bead easier/faster. This is true if you're using CO2 or a compressor.

When using a CO2 tank, you never have to worry about the noise level. The only sound you hear is the slight wooshing inside the tire as it's being filled.

A CO2 setup can be setup can be put together fairly inexpensively, but you'll have to shop for the individual parts. The Power Tank option can be as much as a really good compressor. CO2, no matter how big of a tank you have, is a limited resource. When you're out, you're out. Unheard leaks can ruin your fun when you go to air up at the end of a trail and find an empty tank. Or to run that air tools for a trail fix. Cheap regulators can freeze over and cheap hoses can splinter if frozen for too long.

Refills can be a big deciding factor. Check for availability in your area for this service before buying equipment. It's illegal to fill CO2 tanks within San Francisco. I have a friend who welds and I'll drop my tank off with him to get refilled in the East Bay. You'll have to find a shop that will preferably return your same tank. Some only do a tank swap of what they have in the back room. A 20# tank costs me about $25.

The number of times you can refill your tires will depend on the size of the tire, and pressure ranges (say 15PSI up to 40PSI). The only way to determine how much CO2 you have left is by weight, and maybe shaking to feel for the level of the liquid. A pressure gauge for the tank (not what is coming out) will show full pressure until the tank is empty.

Lastly, CO2 is soluble with the rubber compound found in tires. It permeates through the material and escapes into the atmosphere, thus reducing the tire pressure over time. If you wheel often enough, you can keep this in check due to the constant refilling of tires, and checking the levels. But if you only go out every couple of months, you should periodically check your pressure levels, and consider refilling with air at a gas station.


Air Compressors

These can range from a cheapo unit that can barely fill a passenger tire up to something that can run air tools without missing a beat. There are a few notable companies out there making well thought out and put together compressors; Viair, ARB, Extreme Outback to name a few.

Your typical air compressor will run off of a 12V power supply with a rated PSI (pounds per square inch) and CFM (cubic feet per minute). While the PSI is important, the best way to determine if a compressor suits your needs is to look at the CFM rating, and at what pressure. Just because the box says the maximum pressure is 300PSI doesn’t necessarily mean it can move a large volume of air. Look for a CFM rating around 2 (or more) at 100PSI for a better comparison.

The more amperage drawn by the compressor will mean a more powerful unit. The number of amps can reach 80 or more. So if you’re looking at a compressor that only comes with a cigarette light plug, you’re probably better off leaving it on the shelf at the store. You will also want to run wiring that can easily handle the power rating of the compressor.


Even with a large capacity battery, it’s a best practice to have your engine running when the compressor is running. The increased voltage to the compressor will make it run a bit faster and reduce the amount of load on the vehicle’s electrical system.

A good compressor will be heavy and have it’s own mounting requirements. Some can be mounted in any position, even upside down, in or out of the vehicle. You’ll also need to keep the area around the compressor open to allow sufficient airflow for both cooling of the motor and output to the hose. If there’s an on/off switch it should be easily accessible even when the truck is fully loaded with gear. These factors should be a major deciding point on the unit you purchase.

If you are going to be “the air guy” out on the trail and fill up a bunch of tires, or need to run air tools for a while, you’ll want to take into consideration the duty cycle of the compressor. The duty cycle is how long you can run the motor before it needs time to cool down. A 50% duty cycle at 30 minutes means that after a half hour of continuous use, it needs another half hour to cool down. Whereas a 100% duty cycle can run non-stop. The number of tires you can fill at a time will depend on the duty cycle. And again, the size of tire and pressure ranges for your needs will help determine what duty cycle you’ll need, or should avoid.

Some, but not all, compressors will have built-in pressure cutoff or thermal cutoff to avoid potential permanent damage. There also may or may not be an on/off switch on the unit itself. If not, there’s typically disconnect on the power cables when you want to turn it off.

Expect to pay anywhere from $300 up to $600 (or more) for a good compressor. If permanent mounting isn’t a viable route, many manufacturers offer the option of a kit. These usually come in a metal or plastic case that can house the power cables, airline and gauge and can be removed from the vehicle when not needed, or moved to another vehicle.

Something not always talked about, but worth taking into consideration is the noise level of the compressor. Some can be pretty quiet, but typically you won’t want to hang around and hold a conversation with someone right next to it.

A compressor is a complex setup, with points of failure including the moving parts, and electrical connections. Troubleshooting is more involved if it stops working, and it’s hard to replace just a single part if it breaks.


Summary

As you can see there’s a lot to consider with either option for OBA. Both can be a high dollar investment, so take your time and do your homework on the best option. See what solutions other people have for airing up their tires (or running air tools) and what their experiences are using them. In the end, either CO2 or a compressor is a great addition, and security, to have. It means you will have a better time on the trail knowing that you can re-fill your tires at the end of the trip, re-seat a bead, or perform trail repairs (assuming you carry the right tools for the job).
 

Wawa Skittletits

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Thank you for the comparison. Considering my needs it was going to be a compressor all the way. Small size, automatic function, performance, and duty cycle were my deciding factors when I purchased my VIAIR 400P. My tires aren't OE sized but are still only 245/65 17's so there are no issues there because it was designed to handle up to a 35x12. With the exception of my snatch strap I always prefer to have something more HD than my needs.
 

MOAK

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It is a very good comparison. For us though it is all about stowage. I considered co2 years ago but three major things kept me from switching, size, weight, and the remote possibility of running out of co2. On a typical journey we have to air up 15 or 20 times during the 6,7,or 8 weeks we are out. ( A friend I wheel with on occasion has run out of co2 on two occasions.) I'm liking the portability of the Viar 400p and it is plenty fast airing up my 285s.
 

MarkW

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Great comparison. I have been running a PowerTank for a little over 7 years now and been very happy with it. The two downsides is when it runs out it's out, though I have never had that happen with many numerous week long wheeling trips. The second is finding a good convenient place to get it filled. For a while they only place that I could get to when open to fill it was a dive shop and he could never get more than 5 lbs in my 10 lbs tank. I would like to note though they can be stored on their side as well as on the outside of the vehicle. They must be upright when being used though. I have stored mine on my Gobi rack for years and the past year or so on the ladder where it is now upright and I don't have to remove it to use it. Ultimately, though I have not researched to see if I have the room, I would like to add a York A/C compressor to my truck connected to a tank. Have had a few friends running this setup and you get a lot of CFM and duty cycle is not an issue. I have seen both running air tools for extended periods with no issues or lag.
 
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AlysonH

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Nice write up Brenton.

I have both a compressor and a powertank. Every time I pull out the tank to inflate my tires I seem to make new friends... It also costs me about $25 to refill and I go to a soda carbonation shop in Santa Clara and I get back my same tank.
 

VCeXpedition

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@Disco2Guy, good write-up. I also have both, just upgraded my compressor to a 12V Puma with 1.5 gal tank and mounted it inside. The electrical hookup was quite complicated to meet the power demands of the compressor, but I just did a dry run tonight and with my hoses connected to all 4 tires at the same time, I could go from 18 psi to 44 psi in 12 minutes on 285/75-16 tires.
My co2 is in the middle of my car and is easy to get to, but because of the reasons you mentioned, co2's affinity for rubber and the inconvenience of refilling, the compressor is my go-to with the co2 as a back-up.
If you're around southern California, south bay, Tym's is the only place I've found that's reasonable, quick and you always get your own tank back.
Dan.
 

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A guy in our club popped my bead back on my rim while on a snow wheeling trip. I don't even think we used a ratchet strap so I went to powertank and bought one. I chose the one that they say was the most common size which was a 20# tank. A week goes by and in the mail I got this huge yellow Scuba tank looking cylinder. The one on the trial I used was a 10# come to find out. So now I use this huge tank on the trail and like Alyson said I'm everyone's friend and I'm pretty sure the tank holds infinite amounts of Co2 because it never runs dry. haha. But just to be sure it never runs out I take it to AirGas in Concord a few miles from my house. I love my Co2 tank. It's simple to use and like I said has plenty of "air." My recommendation is, if you're going to go the Co2 route and your not driving a support vehicle for the Dakar, or Baja races go with the 10#. I like my 20# because I tend to hit the trail with some beginners and I like to have enough to fill multiple rigs up and still have a bunch left over.
 

Rob Bradish

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New user, but tanks are something I understand!

I use a scuba tank. It carries 130 ft3 of air at 3600PSI. I use a Medical compound regulator to control the pressure, typically setting it at 100psi outflow, more than adequate to run an impact wrench to change a tire (uses about 500psi to remove two tires an replace them ) and airs up (4) 265/75 r16 tires from 18 psi to 35psi lickity split, about 8 ft3 each (about 1000psi).

Fills are $4-5 from any Dive shop or most Fire Departments.
 

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@fj80toyman - Hey Dan, thanks of putting out the info on Tyms, they're the only one that didn't insist on a tank trade. They've got my tank now for a re-cert and fill up and you were right, their prices are reasonable. Funny thing when I walked up I remembered the trucks from my previous job and needless to say, I kept my sunglasses on and avoided eye contact. Didn't want to end up in the dry ice bin!!! Haha.
 
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9Mike2

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I got mine from a guy on the Wrangler Forum, Nate from Instant Air Supply, He sells the parts if you want to go the exchange route like BBQ tanks. I got the 10# size and have been able to refill my tires two times and both my Daughter's once each and still had Co2 left. Nate at IAS has a website and can set you up for about 200.00. I get my tank refilled at Co2 Giant in Santa Ana and at A beer making place in Huntington Beach about 20.00, the beer making place is pretty cool, but I am trying to save money and not spent more and beer Too.......
 

Adventure-Farmer

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I have a 20 pound powertank and it is great. Fills up tires extremely fast, and it is quiet!
I highly recommend them.
 

Zargon

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While I am not 100% sure, if I remember correctly from my chem classes, CO2 will leak out significantly faster then average air (AKA mostly nitrogen). While the time for vehicles probably varies greately, I know that bike tires will go flat after 2-3 days when running pure c02
 

Captain Josh

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While I am not 100% sure, if I remember correctly from my chem classes, CO2 will leak out significantly faster then average air (AKA mostly nitrogen). While the time for vehicles probably varies greately, I know that bike tires will go flat after 2-3 days when running pure c02
That's true. And I'm surprised no one is talking about combining compressors with air tanks? It can really help mitigate CFM or Duty Cycle issues, depending on what the need is, and how the system is designed. Not magic, but this is the approach I am looking at for my own rig.
 
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