buying impact gun 3/4 or 1in ???

1 inch for sure for wheels. 3/4 is ok, but 1 inch will spins those suckers like nothin'. CAUTION! Be careful when reinstalling. You really should not use a 1 inch gun for reinstalling. Too powerful! Those guns are good for 800+ ftlbs no problem. Standard wheel torque is only 450. You'll over torque ever time with a 1 incher. I see guys all the time use 1 inchers to reinstall and for some reason they let the dam thing rattle and rattle like it is a 1/2 gun. No, no no! You would be surprised how tight those guns get the nuts with just a slight trigger pull resulting in only one hammer of the impact.

 

one inch will run on a 80 gal tank for how long who knows just make sure you have a 5/8 air line might have to wait alittle but should work i only have a 30 gal tank works not the best but gets the job done

 

The problem with an 1" is when you try to use it for anything else besides lugs and suspension parts. When you see one pick it up and pretend you are holding it out and trying to tighten/ loosen the slew ring bolts on your loader. And remember your holding a huge wrench with the other hand. Most places it wont fit. The big mounting bolts holding it to the frame should always be cranked down with a torque multiplier/ 3 to 1. I have NEVER had a lug nut the IR 3/4" didnt loosen. If you did run into this problem, it be cause some knuckle head did exactly what heavy said. You should heat that nut up, then replace the stud and the nut before you mount the rims.

 

Snug them then use deg's, use a torque wrench first to get a idea how far to turn (90 or 180 or what ever) then you can watch the socket as you tighten.

 

I run a 30 gal tank compessor makes 30.2 cfm with a 1/2 inch line on my mechanics truck and have no trouble running a 1 inch or 3/4 I run 175psi by the way. Getting duals off and having to hammer on them I never have to let it catch up, pulling pads off when replacing rails on a machine yeah gotta give it a break often.

 

We have IR 3/4 guns, they are good! We use the 1 inch guns for most wheels because we have simply worn out so many 3/4 guns. For only one guy a 3/4 gun would probably be fine.

 

3/4 will be fine once you put all your lug nuts on properly. Speaking of compressors this is the problem most run into is the regulator. If you regulate the air as your supposed to it wont flow enough to run the gun properly. You may have the regulator at 90 but when your working the gun it may drop to 60 at the gun itself. I've checked it with a gauge at the gun once and yes it was a big 1/2 regulator. That is why most tire shops run straight off the comp. which only add to degrees of being overly tight.
Here is how my air system is set up and it works great. I have 2 tanks the comp tank that has a line off it to air tires and to put more muscle to my gun incase I've had tire work done on the road. The second tank, and its just that a tank, is down wind of the regulator. All my other hoses come off of it so now when my inch gun is running it has all the air it needs without having to over pressurize it.
The second tank is my old comp. that the pump blew up on. Set up this way also helps control water at the hose end

 

I run a 80 gallon compressor and I have 1 inch and 3/4 IR impacts. My 3/4 gun will remove and replace anything on my truck. I think the 3/4 gun is the best all around to buy. You might opt later down the road to add a 1 inch unit for those instances where something was installed wrong or corroded. No worries on the compressor running either one. The 1 inch taxes the compressor a little more, but it also does not take as long to loosen something when using it.