inflating tire, cubic feet of air in tire and in air tank and psi
- Thread starter tony326
- Start date
Mwilliamshs
Explorer
Yep. Only had a CO2 setup a short while but it's been a game changer. Inflates tires FAST. I use a cheap fixed regulator so I'm always flowing 150 psi but do have a cheap inline regulator (think paint gun) for my Simonds crimper (not cheap lol). My HF Earthquake 1/2" impact runs like a clydesdale on this thing. For an idea of volume needed to fill tires, there's a chart at https://www.expeditionexchange.com/powertank/FAQ.php.
As an aside, this thread, not specific in any way to vans or even camping, would likely get more traffic and more, better responses if posted elsewhere. Just an observation.
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proper4wd
Expedition Leader
FYI my napkin calculations put a 235/75R16 tire (guessed at 30x8 size) inus rim at about 1000 cubic inches of volume. logic would dictate this would require 2000 cubic inches of volume at 170psi to fill 1000 cubic inches to 85psi. that would be ~8.7 gallons. 170 psi is high for an air tank, so adjust that down to ~150 and the 10 gallon WAG is pretty close. a 10 gallon tank is huge - like 24x10" cylinder.
Bikersmurf
Expedition Leader
I ran a 30lb propane tank for years. It'd inflate all four 33x12.50 tires from 10 to 25 psi with air to spare. Also one from zero to 50+. They're a standard right hand thread on the tank.
You'll also want a compressor to keep it charged. I traded beer for a Titan compressor that does a decent job with no tank. Some day I'll add a tank and then air tools will become an option too.
You'll also want a compressor to keep it charged. I traded beer for a Titan compressor that does a decent job with no tank. Some day I'll add a tank and then air tools will become an option too.
Bikersmurf
Expedition Leader
24x10 is about the size of a 30lb. FYI I ran mine at 150 psi... I'm sure it could handle more.
http://www.expeditionportal.com/forum/threads/162622-inflating-tire-cubic-feet-of-air
emergency purpose only one time tire fill. tank will be center of van. i need dia. tank, i can fill to 200 psi at home i didnt want to go c02
emergency purpose only one time tire fill. tank will be center of van. i need dia. tank, i can fill to 200 psi at home i didnt want to go c02
Mwilliamshs
Explorer
I'll take a stab at actually answering the original question. A BFG AT KO 235/85R16 is 31.7" tall and 9.2" wide in section. Ignoring the thickness of the rubber, that cylinder has a volume of 7,215.26 cubic inches. A 16" x 6.5" wheel (I guessed, used BFG's "measured rim width") has a volume of 1,286.80 cubic inches, so we'll subtract that from the tire and get 5,928.46 as the volume of the tire itself and that's 3.43 cubic feet. Assuming you've started at 0 psig (14.7 psia), you need a tank of at least 6.86 cubic feet at 85 psig to inflate 1 such tire from 0 to 85 psi. That's over 51 gallons. Larger than the typical residential water heater. Double the pressure and you can halve the volume, so 3.43 cubic feet at 170 psi. That's asking a lot of an air tank. This number is optimistically low, since it treats the wheel as a simple cylinder, and it isn't. The wheel has a dropped center between the tire beads which increases air volume inside the tire.
The tank capacity must be at least double that of the tire and/or the pressure must be higher, or you'll reach equilibrium at less than your desired pressure. A higher starting tank pressure can allow a smaller tank to fill the tire just as well but honestly most air tanks suitable for vehicle mounting are gonna max about 125 psi and that's MAX, so don't go inflating your tank to 125 cold then drive out to the desert. Now for a more realistic scenario, you're probably airing down to 20 or so psi offroad then back up to 85 to hit the highway, which requires only 77% as much air, or 2.64 cubic feet per tire, 82.28 gallons for 4 tires. So basically, a 100 gallon air tank at 100 psi will air up all 4 tires from 20 to 85 psi once. That's a big air tank, like, REAL BIG, as in, very doubtful you'll get that under your van at all. Keep in mind the shape of air tanks; they're cylinders, not rectangles, etc. The 80 gallon tank on my compressor is about 40" tall and 30" in diameter, so laid on its side, it would not even come close to fitting under my van.
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proper4wd
Expedition Leader
Your numbers are off by a decimal point. But the greater point remains, why have a single user, huge air tank that depends on being refilled when you could have an endless amount of air from one of these,
For $40 and just throw it in the van?
https://www.amazon.com/Kensun-YS-20...&qid=1472660659&sr=8-5&keywords=tire+inflator
For $40 and just throw it in the van?
https://www.amazon.com/Kensun-YS-20...&qid=1472660659&sr=8-5&keywords=tire+inflator
luthj
Engineer In Residence
If you are going to get a portable air compressor, one of these will perform much better. You won't get a good fill rate from a cigarette outlet (they can't produce enough power). Plus duty cycle is a factor, so units with big motors and heatsinks will run cooler and longer.
http://amzn.to/2crfPQd
One of these Viair system would work well. I have this model on my sprinter, and I have liked it thus far.
http://amzn.to/2bS560m
The CO2 tanks are great uses of space, they are also easy to handle and small to stow. For emergency use they would be a great option. If you have access for easy filling/replacement they would also work great for regular use on the trails.
http://amzn.to/2crfPQd
One of these Viair system would work well. I have this model on my sprinter, and I have liked it thus far.
http://amzn.to/2bS560m
The CO2 tanks are great uses of space, they are also easy to handle and small to stow. For emergency use they would be a great option. If you have access for easy filling/replacement they would also work great for regular use on the trails.
If you get a 12V compressor definitely get one that hooks to the battery as linked above. Much better than the cig lighter ones, not much more money.