First of all if you are talking about a 12 volt portable and automatic compressor, you need a good one that has good CFM. The only one I know of that is automatic and has these features is Viair. You can buy a regulator and adjust it to the psi you want. Use the appropriate quick connect fittings and get a gauge that has a 1% accuracy or better as many of them have low accuracy. You'd still want to check the final PSI with a hand held gauge (with good accuracy) and adjust up or down as needed. The needed duty cycle will depend on what you are pumping up - big tires to high psi from nearly flat, or just topping up a couple of psi all around. For just topping up, 33% duty cycle is fine.
Q Industries has the MV50 model compressor which is a close knockoff replica that looks like it's made in the same factory as Viair. Internally it's lesser quality & design though. There are a few other alternatives around but don't know anything about them.
What I recently did is buy a used Viair 300P unit ($100 Can.) that has 33% duty cycle and does 2.30 cfm and then modified it. Viair portable automatic compressors can't do more than 2.30 cfm and you can spend a lot more for their 450P-RV Automatic model and not gain anything. I modified the 300P by installing a Viair 90/120 psi pressure switch in the end of the compressor, adding a pressure gauge and a female quick connect fitting. I tested a tire on our truck and pumped from 70 to 80 psi in a little over 90 seconds which isn't that bad I think. I ditched the Viair recoil hose and am using an ultra-flexible 25' poly hose. I added a bleed valve on the hose to release pressure so the compressor won't get stored away with pressure on the head. This kind of modification isn't for everyone though (I like tinkering with stuff).
If you get a small portable 120 volt compressor, I think they are around $100-150 and have a higher cfm. They also come with a regulator & gauge and because they have a tank, aren't running continuously while pumping air. You won't have to worry about duty cycle on a 120 volt portable compressor like you do on a 12 volt one. If for home use, just get a portable 120 volt compressor. I have a Porter Cable pancake type that I've used while on the road in the past and has no problem getting the job done but are awfully noisy.
On chucks and inflator gauges/guns, I initially bought a Viair one and they are cheap junk (in sharp contrast to their compressors). What I found in doing my research is that MOST tire gauge/inflator guns have a low CFM (around 1 psi) and low gauge accuracy. Unless you spend a lot of $$, it's not possible to find a good one. Why have a compressor capable of 2.30 cfm (or more) if the inflator/gauge is only good for 1 psi? Many of them don't even provide specs. For now I'm using an ordinary ball chuck. If you read online reviews, many of the lock-on style chucks that come with inflator guns don't work well and need to be replaced. I bought a lock-on chuck like in 3rd photo that I may switch to. If using a lock-on tire chuck, you must use either a tire inflator gun ("stick" or pistol grip style) or a regulator otherwise will risk over-inflating a tire.
Q Industries has the MV50 model compressor which is a close knockoff replica that looks like it's made in the same factory as Viair. Internally it's lesser quality & design though. There are a few other alternatives around but don't know anything about them.
What I recently did is buy a used Viair 300P unit ($100 Can.) that has 33% duty cycle and does 2.30 cfm and then modified it. Viair portable automatic compressors can't do more than 2.30 cfm and you can spend a lot more for their 450P-RV Automatic model and not gain anything. I modified the 300P by installing a Viair 90/120 psi pressure switch in the end of the compressor, adding a pressure gauge and a female quick connect fitting. I tested a tire on our truck and pumped from 70 to 80 psi in a little over 90 seconds which isn't that bad I think. I ditched the Viair recoil hose and am using an ultra-flexible 25' poly hose. I added a bleed valve on the hose to release pressure so the compressor won't get stored away with pressure on the head. This kind of modification isn't for everyone though (I like tinkering with stuff).
If you get a small portable 120 volt compressor, I think they are around $100-150 and have a higher cfm. They also come with a regulator & gauge and because they have a tank, aren't running continuously while pumping air. You won't have to worry about duty cycle on a 120 volt portable compressor like you do on a 12 volt one. If for home use, just get a portable 120 volt compressor. I have a Porter Cable pancake type that I've used while on the road in the past and has no problem getting the job done but are awfully noisy.
On chucks and inflator gauges/guns, I initially bought a Viair one and they are cheap junk (in sharp contrast to their compressors). What I found in doing my research is that MOST tire gauge/inflator guns have a low CFM (around 1 psi) and low gauge accuracy. Unless you spend a lot of $$, it's not possible to find a good one. Why have a compressor capable of 2.30 cfm (or more) if the inflator/gauge is only good for 1 psi? Many of them don't even provide specs. For now I'm using an ordinary ball chuck. If you read online reviews, many of the lock-on style chucks that come with inflator guns don't work well and need to be replaced. I bought a lock-on chuck like in 3rd photo that I may switch to. If using a lock-on tire chuck, you must use either a tire inflator gun ("stick" or pistol grip style) or a regulator otherwise will risk over-inflating a tire.
