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That is an old wives tail. I have run CO2 for 20 years. I may drop 5 lbs in 6 months.
OB Approved CO2 vs. Air Compressors
- Thread starter 4xFar Adventures
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- co2 compressor oba on board air
Influencer I
Wrong, you are confusing compressed Air with CO2. It is not just about speed, volume counts too, and CO2 has both. Watch the attached video, then look some up on your own....
@4xFar Adventures Thanks for the description rundown of the two main options!
Ok. What is the smallest CO2 tank that can inflate four 37s from 0psi to 30psi? Space is at premium so I am asking for the smallest. Thx.
Influencer I
Need more data:
What is the rest of the tire size, ie. 37 x 12.5 x 15 or simular....?
I assume you want to start at zero because you will be putting a new tire on a wheel on the trail?
37/12.5/17. I'm now on 315/17 but planning ahead. [emoji5]
Inflate pressure from 15psi to 30psi on trail but I said from 0psi for some reserve just in case (ie. seat a bead).
I am looking at minimal space/volume, the smallest co2 tank. I do have an arb compressor under the hood for backup.
Inflate pressure from 15psi to 30psi on trail but I said from 0psi for some reserve just in case (ie. seat a bead).
I am looking at minimal space/volume, the smallest co2 tank. I do have an arb compressor under the hood for backup.
Influencer I
The formula for it’s volume is R squared times D times PI squared, where R is the Radius of the doughnut and D is the diameter from the center of the doughnut across the hole to the center of the doughnut on the other side.
Say your tire is a 37 - 12.5 - 17. The tire is about 12.5 inches across at the sidewall, so R is 6.25. The diameter from the center of the sidewall across the hub is about 22 inches. So the volume of the tire is 6 times 6 times 22 times 9.8696…, but 9.9 will work fine. That calculates to 7841 cubic inches. Divide by 1728, the number of cubic inches in a cubic foot, and you get a tire volume of about 4.5 cubic feet. Of course you can work entirely in cubic inches, too.
To figure out how much air it takes to inflate it, it is easiest to think in atmospheres, or multiples of atmospheric pressure of about 15 PSI. If you shove 4.5 cubic feet of air into your tire, the pressure will go up by 1 atmosphere, or 15 PSI. If you want to air up from 10 PSI to 25 PSI, put in 4.5 cubic feet. To bring it up from totally flat to 25 PSI, or increase pressure by 1.67 atmospheres (25/15), will take about 7.5 cubic feet – 4.5 times 1.67.
And how big a tank do you need? Lets say you want to air up your 4.5 cubic foot tires from 15 PSI to 30 PSI. That’s an increase of 1 atmospheres (15/15), so you need 18 cubic feet of air (1 X 4.5 X 4). If you fill your tank to 150 PSI, that’s 10 atmospheres. Air will stop going into the tire when the tank pressure equals the tire pressure of 30 PSI, or 2 atmospheres, so you have 8 atmospheres available. Subtracting one more atmosphere will leave about 15 PSI in the tank when you finish, so with a reserve you have 7 atmospheres usable. Consequently it will take a 2.57 cubic foot tank (18 / 7). ~ calculations from Jim_Lou from off-road.com and modified by me to meet your criteria.
The conversion rate from liquid to gas from a CO2 tank is one pound liquid = 8.741 cubic ft of gas, so a:
5lb CO2 cylider would hold 44 cu ft. @ 850psi
10lb CO2 cylider would hold 88 cu ft. @ 850psi
20lb CO2 cylider would hold 175 cu ft. @ 850psi
So, for every pound of CO2 you would get 3.4 fills (4 tires from 15psi to 30psi) ie (8.741 / 2.57).
Or, a 5lb CO2 cylinder would give you 17 fills (4 tires from 15psi to 30psi) ie (8.741 * 5 / 2..57).
It looks like 5lbs will give me what I want plus a couple of extra friends on the trail. Hahaha.
Thanks for the math, Sir! I appreciate the effort.
Now I hear that there are stores who cater to people that enjoy making their own beer at home, and they have fair priced small co2 tanks. Any one has experience with those tanks?
Influencer I
I just like to understand things fully. Try Craigslist in your area for CO2 Tank, Bottle, Cylinder, etc... You are apt to find some deals there. I bought 5 20lb aluminum CO2 tanks for $100 off Craigslist.
Also, if you search Amazon for new 5lb CO2 tanks you'll find many. Also on Amazon you can find a fixed 150psi CO2 regulator for not much, just a little more and you'll be on the trail....
Good luck and let me know if I can help.
No, he was asking about a compressor and tank, Straight air! Co2 with a tank would be by lbs. not Volume, and Co2 is a liquid in stored form not a gas, that's only in when it get into normal air, 14.2 lbs Baro. or less. . I have a 10 Gal Co2 that will fill my 35's twice and both my Daughter's Jeeps stock size with some left over. The same 10 Gal tank with air won't fill two tires back up...
Hey, thanks!
I am putting together a 4wheel inflation/deflation system but that'll take a while cause I like hiding things out of view. I like running cables and stuff to the rear through inside the frame, it also protects them. I can build that system and make it work with the compressor first, then I add the big cherry on the cake -> CO2! [emoji106]
I have what is call a spyder web, that you hook up to all four tires at the same time. You can deflate or inflate all four to the same psi. It has a regulator on it so you can set your pressure and leave it alone...You can make one, go to Trail Recon on Youtube, and Brad, has a video to walk you through steps to build one....
I got my Co2 setup from IAS, a fellow Jeeper on the Wrangler Forum. he runs specials and gives discounts the members on the Wrangler forum . I like helping small businesses . He does them in lots and tries to get you the latest tank certs too. He use to do colors, Powder coating but it became costly, and he's trying to keep the costs down.
I watched that video and it is cool.
But I do not understand why they believe that by using 3/8 instead of 1/4 hose they will get more air to the wheels. The single arb compressor cuts off at 90psi and the air goes out through a 1/4 fitting. So whatever the hose thickness they use the volume will be the same with that setup unless the air pressure is increased.
Yes, your right. I was thinking Brad used smaller air line because it's cheaper and rolls up easier, so it can be stuffed in a smaller space.
I like the idea of having pressure right then and there with a powertank but at the same time I prefer to have a compressor so that I can run my air tools and such for those just in case moments or to help out any fellow traveler that is with me.
Boostpowered
Rank VI
Member III
Well after reading this i feel silly, i only have a 150psi compressor from harbor freight it has done what ive asked of it. Ive filled my tractors 8.3-22 r1 lig tires numerous times without a problem.
Off-Road Ranger I
There is also the factor the CO2 will introduce moisture in to the tires which can cause rotting(from the condensate, you have seen the frosting right?). In Aviation & now some tire shops use Nitrogen. If I remember right it is less expensive then CO2, it is dry & the molecules are larger, thus taking longer to seep out then compressed air.
But you can't compress Nitrogen into the same volume as CO2 so your tank will not last as long
