Air tank to inflate tires

I take my taco out in the dunes alot and most of the time I need to air down to 18lbs. Does anyone know how large of a spare air tank I might need to air up my tires to around 40lbs after I come out of the dunes? I usually air up at a nearby market but sometimes I can't do this and was wondering if I could just carry compressed air in a tank to fill up afterwards.

 

If you don't want an onboard compressor you need a Co2 tank. PowerTank makes them

https://powertank.com/

 

Warning: rounding ahead, so answers are approximate.

A 33" tire on a 17" rim with a 12" width has approximately 7500 cubic inches of volume. PV=PV, so to take a 7500 cubic inch volume and increase its pressure from 18 to 40 psi is 7500*22=165,000 (ignore the units for now). Assuming your tank is a 150psi max, and you don't want to go below 50 psi in the tank, because it'll take forever to fill up a 40psi tire with a 50 psi air source.... you have 100 psi to work with. 165000 divided 100 is 1,650 cubic inches of air. Convert that to gallons and you get just over 7 gallons. As you take air out of the tank it will cool it off, so you'll lose more pressure than what these numbers show. I wouldn't go smaller than 10 gallons at 150psi, and I would verify that in your driveway before you have to do it on the trail.

 

I bought one of these and it has worked out well. Clips to a 12V battery and for ~$140 I don't think you could get better quality. Check out the reviews as it looks like the top reviewer has your exact same use case and offers his feedback. Worth considering. Every time I bust this thing out at a gas station to top up my tires I get construction guys asking where I got it. Napa son.

I ran a VIAIR setup in my diesel rig years ago and had the 5 gallon tank and installed air chucks on both nerf bars - that was nice but a pain in the ass to install and regularly maintain. The only reason I would switch from my current setup is front and rear air lockers.

 

All-top makes a decent "off brand" one but VIAR has a ton of options from small sedan tire models to 100% duty cycle high end pumps

 

ill second the 12v compressors. There are definitely cheaper options like the Napa one above. I picked up this EZ Flate M.O.A.B Compressor and Recoil Hose System second hand on a recent trip and have been very happy with it. The compressor looks almost identical the the Napa unit listed above but it's a solid $100 less. More flate also sells similar compressor and hose systems. These pumps are quick and since it's not mounted they can be moved between vehicles

 

I also carry a compressor. I think it’s the easiest choice, all things considered. Definitely not the nicest set up but it gets the job done.

 

Not sure if there's any meaningful difference between any of these compressors. They have the same output, the same form and function, same CFM. The Napa one is now listed as a "300 liters per minute" because that sounds so much better than 10.5944 cubic feet a minute. The only thing that seems to differ between brands is the paint they add to them and the warranty. Napa's is $122.50 shipped, less tax with the myriad of 20% off coupons they always have.

Edit: Someone on reddit makes the case that the Moreflate is in fact upgraded from the basic chicom 10.6 cfm, and that for single tire filling the 10.6 cfm might be excessive.

Good thread overall:

Those of you with onboard 12v air compressors, which did you buy and are you happy with it? It's time to add one to my trail beater. : r/4x4 (reddit.com)

 

My truck has a Viair 450 series hard mounted in the crossbed tool box - the box has a heavy cable wired directly to the battery for high amp power. I wired the compressor to be regulated with a pressure switch that keeps it at or below the 100% duty cycle. There is a small receiver to allow a bit of surge capacity - keeps the compressor running as I switch between tires.

These 12v compressors are a pretty heavy electrical load - so I always run the engine while its in operation.

 

Just another option - Milwaukee's M12 compressor does the trick pretty well if you've already got batteries, and it's about the size of a can of coffee even with a high-capacity battery installed. Not the fastest thing in the world, but it'll air up a tire from flat to 100% in about 5 minutes, and even on the small battery it can do that twice. Haven't tested it, but I'm pretty sure it would have no trouble airing your tires from 18 to road pressure.

I wouldn't buy it as the permanent solution, but I keep it in the back of my car as part of my emergency kit anyhow.

 

The m18 version is much quicker, and could be used as a permanent solution
It was on sale for a while with two batteries and a charger for $200

 

Yeah, but to be honest I'd prefer a wired-in one that I don't have to worry about checking battery charge on before I leave as a permanent solution for onboard air. TBH the best option as an interim solution between those two is whatever battery system you already have plenty of.