[Kanman]

Not sure where to put this question....

I've been shopping for a new air compressor, and I need some help making an informed decision .

120v preferred general purpose home/shop electrical current only. Nothing too fancy here, cost is definitely a factor.

Compressor 1. 40 gallon single stage 150psi max.

Compressor 2. 60 gallon single stage 125psi max.

Which of these two compressors will do a better job inflating 2 semi truck tires to 110psi simultaneously, and why?

Which factor is more important for me. Volume or max pressure???

Now lets assume both tires are pre-aired to 90psi already. Does this change which compressor will be of greater help to me?

Also: what does jumping from a single state, to a two stage compressor gain me?

[ad64075]

You may want to consider each compressor's CFM rating. This will be most important for your project. Most compressors are rated CFM @ 90 psi, and I would guess the two you are looking at are around 9-11 CFM. The next thing to consider is the plumbing. You need to determine what diameter lines you will be using and the composition of the lines, as well as the size of any fitting the air has to travel through. Rubber lines will generate about 1 psi. loss per linear foot, and this needs to be taken into account when making the best possible choice.

I will try to make some assumptions to help you:

Using 3/8" hose and hardware, rubber for 15 ft, then a steel T, then 2 pieces of rubber hose 10 ft each. This cuts 125 psi to 100, and 150 to 125 at the nozzle. The plumbing is therefore capable of 46-47 CFM. The restriction will be the air entering the wheel through the valve stem. But considering you're working with two valve stems instead of just one, it's a wash. Only running 1 wheel for inflation cuts your CFM requirements to around 36.

An efficient, single-stage air compressor will deliver close to 4 CFM per horsepower, so you're looking at a 12 horsepower compressor!?!?!?

Sounds crazy, right? Truth is, you will not be able to keep up with inflating tires of large volume one at a time, much less two. Your best bet would be a compressor rated with the highest CFM you can find within your budget. Chances are you'll find one about 12.5 @ 110 psi at most farm stores for a reasonable price, and that's about as good as you can expect for home use.

Two stage compressor means simply that one cylinder compresses air into the second cylinder for further compression before being pumped into the tank. Not of any real benefit for your situation.

[txcncman]

You need to know CFM.

[ot1]

Consider a 2 cylinder upright compressor with 60 gal tank or bigger, and 2 hp motor or bigger, cast iron cylinders, oil crankcase. Are you filling tires everyday? How many a day?

[Kanman]

Is the answer to this stepping up to a full blown 220v 200psi shop compressor capable of running the piggiest of DA Sanders? I will if I have to...

I've also noticed there are air compressors with totally different ratings strictly for the airing of tires. Could this be what I really need? They generally have no tank and no limit switch. I have also been looking at Viair's 12v compressors, might be a real solution?... The rest of stuff google has found me in this category looks like Harbor Freight rejects straight of a Chinese junk, or free gifts for opening a checking account.

I'm not filling tires everyday. Just topping off tires on my semi truck and trailer when I am around the house. I have an older Craftsman compressor that cuts out at 125psi, and won't come back on till its clear down to 90psi. It may just be warn out. It's barely enough to fill one 285/75/22.5, and a pancake style compressor for carpentry stuff, which is of less help. But, since I have installed a Dual Dynamic's Crossfire system, which ties the two tires together to equalize and monitor pressure between the two tires. It just won't raise the Psi over about 90 - 95psi.

[ot1]

I suppose this isn't the proper forum for this discussion, and I don't know how the crossfire system works, nor have time to research it, but if the air pressure is equalized in both tires, I hope there are check valves to prevent losing pressure in the opposite tire when one tire fails.. I see carcasses laying all over the highways during the summer in southern states. Losing both dualies on a loaded trailer could be pretty dangerous. What is the inflation pressure of your tires?

[underthetire]

There are some realllllly nice 12vdc compressors that can be mounted on board. They ain't cheap, but would run some of the biggest air tools, so inflating a tire would be no problem. The ones we bought would fill a 20 gallon tank from 0 to 130 in less than 30 seconds!
You can adjust the pressure switch on your crapman so it turns on a little higher BTW. I can fill our motor home tires with my cheap harbor freight compressor all day long, but its a cast iron oil type.