I'm planning on installing an on board compressor system on my F-250 to inflate tires after coming off the beach. The compressor will be electric and mounted, along with storage tanks, under the vehicle. Anyone have calcs to estimate the amount of air storage I'll need to fill four LT265/70R17 tires from 15 pounds to 60 pounds without the compressor coming on? The tanks will be charged to 125 psi. Assume air temp is 80 deg F.

 

i would find a friend or a nice samaritain who has a 15 or 30 gal air tank compressor and pump it up to the safe max pressure and turn it off and air up one tire as many tires u can from 15 to 60 psi and that might tell you how much capacity u need or how long you will hafta wait for the compressor to pump back up. im not good at calculations but thats what id do

 

Okay, I'm not great with this stuff but I'll try to give you a general idea. IMO you're not gonna get it to work without the compressor running. But, let's see how the numbers look . . . if I calculate right. And if anyone sees a screw up here feel free to point it out. Numbers confuse me, especially when I'm drunk.

Your tire requires approximately 3 cubic feet of air empty. "Empty" the atmospheric pressure is 14.7 so at 15PSI you have about 6 cubic feet of air in there. To get 60PSI you'll need an additional 9CF of air per tire. Hence we need 36 cubic feet of air to fill all 4 tires.

A 10 gallon tank pressurized to 120PSI will hold roughly 10.6 cubic feet of air. However you have to remember that the tank can only fill the tire as long as it has more pressure than the tire contains. So to fill a tire to 60 PSI you can only use about half that tank (roughly 5 cubic feet of air). A 10 gallon tank (pretty good size tank) at 120PSI could not bring even 1 tire to 60 PSI.

Invest in a GOOD compressor with a 100% duty cycle. I recommend Viair but there are others too. Expect to pay $200+ so you don't kick yourself later.

 

A Viair 550C rated at 2.9 cfm, 150 psi max, 1/3 HP, 30 amp draw with a 100% duty cycle. Can be had for a tidy sum of $299, to play in the dirt comes with a price. Have you considered a 20# CO2 bottle with regulator and hose?
Years ago in Mexico we used a scuba tank to air up as we had a scuba tank compressor for our dive refills.
.....=o&o>.....

 

Beemer Nut has a great point too. Check out the Power Tank: http://powertank.com/

They use some mods in their regulator to keep it from freezing during rapid discharge. If you want some real world experience in it try contacting "Kubota Orange" here on FTE as I believe he's using their system. CO2 is very cheap to refill (any welding or gas shop) and one tank will last you a long time, plus it's portable so you can use it in any rig. These are very popular in the offroad community for people with tires up to 49" which need a LOT of air to fill.

The other option for an on board compressor is to use an older A/C compressor (York) and a small air tank. The A/C compressors will fill a tire very rapidly. However, on the newer vehicles such as yours it's very hard to make room for them under the hood.

 

hehehe.. i ain't gonna bother repeating what i heard really confuses you when you are drunk.




i used to have a 30 gallon tank mounted in the back of the 90 service truck. you could only air up 2 tires without firing up the compressor.

 

Thanks guys for all the ideas. I tried SoArkSI's idea with my home 30 gallon compressor. Starting with 140 psi stored and power off and all four tires aired down to 15 psi I was able to fill three tires to 60psi and the fourth to 50psi all in a relatively short time span. I going for the ExtremeAir continuous duty compressor and will find room to mount three 10 gallon tanks under my truck and I'm sure that will do the trick.