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How big of a air compressor do you need for a impact driver?

After some discussion I am thinking of getting a air impact driver rather than an electric one for removing lug nuts and associated things on my car. What size air compressor should I get? I would prefer to get one small and light. I don;t have much experience with air compressors but know that once you use up all the air it loudly “recharges”. While it is recharging can you still use it or do you have to wait until it is recharged to use it again? I want to be able to take off the lugs nuts on all 4 tires without having to wait. Will a 3 gallon air compressor work?

Here’s the rule of thumb when purchasing an air compressor.

You want the highest SCFM @ 90 PSI (Standard Cubic Feet per Minute at 90 Pounds per Square Inch) that you can afford.

Every Pneumatic tool hogs a lot of air. And a compressor that delivers the pressure but not enough volume of air can make a pneumatic tool useless.

For example, the compressor I have delivers 7.5 SCFM @ 90 PSI.

This will keep ahead of my impact gun. But when you get into higher RPM tools, it just barely keeps up.


@Tester Will a air compressor keep pumping out air while it is charging?

An air compressor must put out enough air to meet the requirements of the tool it’s operating or the tool will need more air than the compressor can provide . When this happens the tool stops functioning .

You won’t need much of a compressor for lug nuts. I have a small oil free one from Sears/ Kmart. I think it’s a 13 gallon and it was on sale for $100 when I bought it six years ago. I have a $29 Chicago Pneumatic half inch drive. Don’t get a smaller one unless you need an air ratchet. I have the 125 PSI compressor, Companion brand. You can use the tool when the compressor is running.
Blowing air from a nozzle is useless but impact guns work well. 7 gallon. Just checked it.

I had an oil-less air compressor, it lasted 2 years in a hobby shop. I have been using a Husky belt driven compressor for 15 years, it has a 26 gallon tank and the rated output is 5.8 SCFM @ 90 PSI. I can remove two wheels before waiting 30 seconds for pressure recovery. Anything smaller would be frustrating. When investing in equipment like this you want something that will work with air ratchets, die grinders and an occasional sand blaster.

Perhaps it is bast to start out with that $40 electric impact, an acceptable compressor will cost $200-300.

Yes you can still use the gun when the compressor is running.

The pressure for the gun is usually set to 90 psi while the compressor will kick on at roughly 80-90 or so depending on the brand. If the gun is an air hog, you may have to wait for the compressor to keep up if the pressure drops below 90 psi.

Unless you are a NASCAR crew member, you likely won’t be able to remove all 4 wheels fast enough to out-run even one of those little pancake compressors.

I agree with @Tester, buy as big as you can afford or have room for. You will find all kinds of uses for one once you buy it.

I replaced the 20 gallon tank on my 30 year old, 3.5 hp Campbell-Hausfeld compressor years ago with a 60 gallon (?) industrial surplus tank. My compressor doesn’t run often, but when it does, it runs for quite a while!

While bigger is better, I got by with a small one with a tank (got to have a tank) for lug nuts and other light duty work. $100-$150 would get a big enough compressor for light duty work like this.

But if I didn’t already have the compressor, I’d go for a $100 electric impact wrench instead, to save room.

Think of THIS also.
Since you have conceded to buying an air compressor for one tool . . .
that opens up the possibilities for a slew of other pneumatic tools that you might want in the future.
Will this new compressor drive those too ?
Because now you can think of home tools too like nail guns and paint sprayers as well as the list of automotive tools.

Buy a compressor . . just once . . that will meet your future needs too.
Now that you own an air copressor . . . put it to good use.

My old Campbell Hausfield belt driven 2 cylinder with a 10+ gallon tank has been in my home shop for 20+ years and on several occasions it kept me limping along at my business when the big compressor failed. The airless models just didn’t seem to hold up very well for me either.

Chicago Electric #60380 from HF $100.00 my go to lug nut remover, DIY tire rotation, brake check. Never bother with sitting up my compressor/hose/oiling air gun etc.

On the other hand if you need a compressor for other tools that’s great but for lug nuts electric impact much handier.

My spiel on this, in case it helps : I was asking myself if an air compressor is worth getting with a 1/2" impact wrench. Naturally, I asked how many other tools can I use with the compressor…

(Why don’t carriage returns work here?? Ugh!)

From a mostly observational perspective - no math : 120V wall power is going to at best get to “3.0” HP (the Makita). They claim ~6 SCFM at 90 psi, IIRC. That’s about as good as it gets for 120V power. Maybe I’m wrong.

The next class (my own nomenclature, nothing official) is the ones that need an electrician to wire it in, which gets up around 10 SCFM.

Obviously that’s very non-specific, but it changed the game for me - e.g. to get the most tools running off the compressor, I’m asking for one of those 10 SCFM machines. Someone said it before : you can never go wrong with more air. Then I ruled out sandblasting because FML I can pay a guy $10 to run the trailer compressor and leave all that mess at his place…

… but I’m rambling again…, sort of a pointless comment, but it’s free.

I still have an old oilless Sears 20 gallon unit. It sees fairly regular use but in the beginning, it was all I had and it ran all the time. Never had any trouble with it. It was good for most of the tools with the exception of high flow stuff like die-grinders, painting or sandblasting. There it limps along. It can still work in a pinch but it is not ideal by any means. It is fabulous as a transportable unit. However, it is LOUD.

BTW- if you want to do any painting or sandblasting beyond one of those dinky little reservoir jobs and have ANY humidity in the area, then you’ll need to rig in a water separator. Good idea anyway but essential for those operations. I also run two separate lines in the garage; one w/lubrication, the other not (painting, blasting, airing tires etc)…

Impact wrenches are air-hogs. Match the numbers or you will be spending a lot of time waiting for pressure to rebuild.

Rod Knox- airless compressor, really? I know you meant oil-less, it just struck me as funny.

In my experience, an impact gun is one of the least demanding of my compressor. It runs very short periods at a time. Unless you have a pancake tank, it should not require lots of downtime waiting. Something like a die grinder or cut off tool that runs non-stop for long periods- now that is an air hog!