unterhausen

I'm mostly asking this because I want to make sure I go bigger. I read about CFM and now I'm more confused than ever.

The 3M paint gun suggests 13cfm at 20psi. Which is a pretty big compressor.

Nessism

I've painted lots of frames, both bike and motorcycle, as well as motorcycle gas tanks and stuff like that using a 2 hp 20 gallon compressor. I'm not sure but it seems the HVLP guns are the ones that need tons of air. I use conventional guns.

8aaron8

Long ago I had good success with cheap Home Depot guns and a 20-gallon 2hp compressor like Nessism mentioned. Today I use a 60-gallon 5-hp compressor, it states that at 40lbs of pressure it puts out 13.2CFM's, the guns I use are mini-guns so they take anywhere from 4-6 CFMs. This combo has worked quite well for me. I believe the general rule, though don't quote me, is to take the maximum CFM of your tool and multiply it by 1.5X to determine the minimum CFMs you need to provide it. I can say that when I was using the 20-gallon compressor it would turn on quite frequently so theoretically at those moments my spray gun was underpowered. Unless you have the gun already, you don't need a full size automobile spray gun to paint bike frames, they tend to be air hogs.

Doug Fattic 

There are several factors involved with choosing a piston type of air compressor including whether it is a single or two stage. It also can make a difference on how big a tank you have. A single stage compressor puts out a higher volume of air but at a lower pressure. The advantage of a 2 stage is that it takes longer to unload the tank before the compressor has to start again. You are never going to regret getting more CFM or PSI. You will regret not getting enough. If ever you get a sandblaster you want as much air as possible at a higher pressure. Cheaper suction types need to operate at at least 80 PSI so you start at the limit if using a single stage. So obviously a two stage works better for sandblasting.

I have 2 Quincy 5hp two stage compressors. I only run one when I am painting (I can use both when sandblasting). With an 80 gal tank I can usually do a entire coat of paint on 1 frame when the tank is starting at 175 PSI before I run out of enough air (in other words until the tank gets down to having 25 PSI). You will remember that I use paint guns with 1.3 or bigger nozzles too. Don't forget to get Hi-flow connectors. I like aluminum ones (available at Home Depot and many other places).