OBA - How much does an air tank help?

[monkeyodeath]

Sorry if this is a basic question, but after a bunch of searching I'm having a hard time getting a straightforward answer:

I've got a first-gen Tacoma on 33"s. Right now I use a Viair 300P to re-inflate my tires. I do not use air tools.

I notice that a lot of folks add a 10 or 20 gallon air tank setup to their OBA system. With a small-ish compressor, does this have any real benefit for tire inflation speeds?

Seems to me even if I had 125 psi built up in the tank, that would get me like 3/4 of the way through one tire at most. So, maybe save 3-4 minutes?

Been pondering giving my Viair a more permanent mount in my truck to save a little space, maybe wiring it in permanently so I don't have to fish it out of my toolbox and pop the hood every time. Figured at first that this would be a good time to add a tank, maybe some lines w/ some remote fittings.

But space is really tight on a Tacoma and I'd rather not spend an entire day trying to shoehorn a tank under the bed if it's going to save me like 2 hours total of inflation time over the next few years.

At first glance it seems to me like this is a better option for folks running air tools and using beefy compressors, but maybe I'm missing something?

 

[Herbie]

You're in the right ballpark on your estimate of the useful volume of a tank as far as airing up. A little time with Boyle's law, a calculator, and good estimates of the volume of each of your tires would tell you exactly how many tires (or portions of tire) could be filled by a given tank at a given pressure.

I run my OBA tankless, and I use an inline-pressure regulator set to my desired tire pressure so that as each tire comes to target pressure, the pressure switch shuts off the compressor. This makes filling a very fire-and-forget activity, which gives me time to do a walkaround inspection on my rig, etc.

That said, there are OTHER advantages to having a tank: If you ever need to seat a bead on a tire - the high volume of pressurized air makes this possible. Seating a tire with compressor only will likely be unsuccessful, unless you get into the field-expedient techniques involving fire and volatile chemicals, which I don't recommend.

 

[sideburns]

Air tanks do almost nothing to help for airing up tires, they're nice if using air tools, even just an air nozzle. Also most people use a 2-5gallon tank, unless they plan to run lots of tools and have 100% duty cycle compressors. Most compressors, like your viair don't recommend over a 5 gallon tank because they don't have the duty cycle to fill it.

I use dual Viair 425c compressors with a 2 gallon tank, fast cycling, and just enough to run an air tool intermittently if I need to.

 

[CFMGarage]

Herbie could not have answered this better. I only added a tank to my OBA setup as there were other benefits.

Air tools need compressor CFM. Any serious use of those requires an exponential upgrade for the compressor (engine driven, Oasis, etc.).

 

[IdaSHO]

I integrated a tank into my OBA setup for one reason....

For blowing stuff off. With an air nozzle, its worth its weight for cleaning out the cab, steps, dusty cloths/boots, dusty dogs, etc.

I don't bother with anything air for tools. Lithium all the way these days.
Hell, with the single exception being sanders and spray guns, I don't even use air tools in the shop!

 

[Smileyshaun]

You're in the right ballpark on your estimate of the useful volume of a tank as far as airing up. A little time with Boyle's law, a calculator, and good estimates of the volume of each of your tires would tell you exactly how many tires (or portions of tire) could be filled by a given tank at a given pressure.

I run my OBA tankless, and I use an inline-pressure regulator set to my desired tire pressure so that as each tire comes to target pressure, the pressure switch shuts off the compressor. This makes filling a very fire-and-forget activity, which gives me time to do a walkaround inspection on my rig, etc.

That said, there are OTHER advantages to having a tank: If you ever need to seat a bead on a tire - the high volume of pressurized air makes this possible. Seating a tire with compressor only will likely be unsuccessful, unless you get into the field-expedient techniques involving fire and volatile chemicals, which I don't recommend.

carry 2 ratchet straps with you and put them just inside of where the lip of the rim sits andget them just a little past snug , it will push the tire enough to get it against the bead and seal it up allowing you to get air in even with a weak compressor

 

[monkeyodeath]

Awesome advice, thanks everyone. I do like the idea of being able to get a little air spray action to clean stuff out, and I've been pondering building a low-pressure circuit to drive an outdoor shower/faucet from a Scepter can -- tank would be helpful with that.

But good to know it's not really necessary for the main objective -- filling tires. Might crawl around a bit beneath the truck bed and see if I can find a spot to stash it.

 

[XJLI]

CO2 is the fastest tire filler (seconds, not minutes), but I wouldn't run that tank under the truck.

 

[4000lbsOfGoat]

I carry a 10lb Power Tank in a Track Bag in my Tacoma. It fits nicely on the floor behind the drivers seat. It'll fill a 275/70/17 from 20psi to 35psi in about 20 seconds. No wiring, no hoses, no hassle. It just works every time.

If filling tires is your primary concern (as it is mine) then I recommend staying away from the complexity required of a hard-mounted and plumbed compressor system.

 

[Tumbleweed]

The above posts cover it fairly well. I have run OBA on every 4x4 I have owned over the last 25 plus years. Most had a small air tank. My current truck has a portable compressor with no tank. This truck does not have a very good choice for mounting the compressor and tank. I do still have my one gallon portable tank plumbed so I can have it in line with the compressor or not. I use quick disconnects. This also makes a convenient tiny air tank for a wheel barrow tire, bicycle tire, etc. I also use a coiled HD air hose that is 25 ft long which does hold a tiny bit of air volume. I use the same hose that semi's use for hooking trailers to the tractor cabs. These hoses won't freeze and crack, and are pretty much tangle proof. They are pretty bullet proof for what I use them for. I do use a blow nozzle, and the hose seems adequate for what I need-as long as I am not in a hurry.

 

[monkeyodeath]

I have considered CO2 before (mainly cause I have a tank from a homebrew phase from a while back), but not really excited to have yet another consumable that I've got to keep track of on the truck. Honestly I'm not too particularly bothered by the slow fill times of the Viair, at least for the kind of wheeling I've been getting up to lately.

Might poke around and see if there's somewhere I can shoehorn a little air tank under my truck, cause I do like the idea of having a little extra for blowing stuff off. But given the feedback above, not gonna try too hard.

 

[broncobowsher]

A storage tank will allow the compressor to keep running and making compressed air as you check tire pressures and move from one tire to another. But to keep in mind the duty cycle rating of the compressor as this may not be a good idea, or it is a great idea.

The ratchet strap tire seating trick sometimes works. High volume air is typically needed as well. If you can't get a perfect seal for 720 degrees of bead seat (both beads at once) you will never get the tire to seat again. Even with straps you may only get a split second where all the beads touch at once. Once all the beads are touching at once you need pressure to hold them touching and allows pressure to build. That is where high flow air is key to seating tire beads. Don't care if it is the tire shop or on the trail. It will be an exercise in futility trying to hold most tires just perfect (with or without a strap) while waiting for a small compressor to build enough pressure to start the seating process. That is where you need a blast of air. A lot of tire machines have a bead blaster to help with this. It blasts a puff of air into the bottom bead and the rebound catches the tire and seats it. The field trick is starting fluid and fire. Lacking either of those, pulling the core and using an on board storage tank is your next best bet.

So you see people putting 10-20 gallon tanks on. Nobody says you have to go that large. A little 2-gallon tanks can work as well. Places like seamlesstanks.com have all different sizes to fit all kinds of different places

 

[1stDeuce]

I had two ~10 gallon tanks on my old Stepside Chevy, hiding under the rear fenders. I did not have a compressor at all, but those two tanks plumbed together allowed me to air upall four tires from 15psi to a little over 25psi, IIRC. That was enough to get me down the road to the next gas station so I could air back up to proper pressure, and refill the tanks for the next outing. (Using a real compressor.)

I would agree that a tiny tank offers no benefit for airing up if you are using a 12v compressor. My GMC has a Viair 400c 12v compressor with no tank aside from the line volume, and quite frankly, I wouldn't want one with a 12v compressor, as a tank only adds to the time to air up tires by increasing the volume that must be inflated to a given pressure.

I have a ~3 gallon tank on my Jeep, running the A/C compressor for OBA. While it will run an air impact in very short bursts, it's otherwise pretty useless aside from acting as of a buffer for the system. When I installed it, I was worried that with only the hose volune to fill, the compressor would go over pressure before it shut down. The tank does come in handy for airing up the occasional mtn bike tire without having to start the Jeep though...

In all my years of wheeling, I have never pushed a tire off the rim, even when running dunes in the mid-single digit range. I tend to run wheel widths a few inches less than the tire width, so that the beads pretty much seat on their own, even with slower 12v compressors. If your tires won't just "air up" when the beads are not set without the help of a big tank or starting fluid, your wheels are simply too wide, IMHO.

 

[RoyJ]

Air tank depends on how robust your compressor is - with an ARB twin, or twin Viair 480/485s, you gain some extra air in between tires, as the compressor continue to work. The extreme would be an Oasis or York, it'll probably fill a 5 Gal tank to the max in between tires...

On the other hand, if your compressor is barely adequate, like a Viair 88p, the extra tank would hurt thing by over-taxing the small compressor.

 

[Wiley556coyote]

I just wanted to throw out something completely different that has totally changed my perspective on inflating tires with a little electric compressor. I have the cheapest smittybuilt compressor and it inflates my 33s in less than 10 minutes with zero effort, I just clip the Quad inflator on, and sit back and relax for a few minutes. It's awesome for deflating too, super fast. You can turn off the compressor and it will perfectly equalize the tires too, or take off just the front or rear inflates and then add a few more psi to the other set of tires.

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