I noted that someone was looking for this information recently, and I thought if someone was, there may be more folks trying to get some tips on the process.
In order to fill tires, you need a compressed air source. In this case, let us assume that it is the home air compressor that is being used?
What is the air pressure in the air compressor tank? Typically, a smaller air compressor will run until the tank pressure gets to 100-150 PSI, somewhere in that range. Let us assume then that our air compressor has run up to the cut out pressure, and we have 120 PSI in the tank.
Having pressure in the tank is important, as compressed air flows from areas of higher pressure to areas of lower. If the pressure in the tire was, for example, 35 PSI, and the compressor tank had only 20 PSI in it, and the air compressor was not running, the air would flow from the tire back into the air tank through the air hose!
With a fully charged compressor tank with 120 PSI in it, we will need to connect an air line to the compressor discharge coupler, using a connector that fits that coupler. At the other end of the air line will be another coupler. The coupler will not let air flow out until a mating connector is inserted.
You have a tire chuck? That’s the small tool that fits over the valve stem on the tire, when it is pushed down onto the valve stem, air can flow through the tire chuck into the tire. So, you need a tire chuck, and you need one that can have an air connector threaded into it, since without the air connector, you will not be able to attach the tire chuck to the air line from your air compressor.
Air line connected to the discharge coupler and tire chuck installed on the other end of the air line? Good, now, push the tire chuck down onto the tire valve stem. You may have to remove a threaded cap off the tire valve stem first.
You are now blowing compressed air at 120 PSI into your tire which will way over pressurize the tire. What pressure do you want for that tire when it is full of air? How will you know that the tire is full to the correct pressure?
One is to set the regulator on the discharge pipe from your compressor tank to the tire pressure setting you want the tire inflated to. If you set that regulators to, say, 40 PSI, and the air tank has 120 PSI air in it, the regulator will reduce the pressure flow to the tire to 40 PSI, or whatever pressure you set the regulator too.
The other way, and the one I use, is a tire pressure gauge. I watch as air is flowing into the tire, and when I think it’s getting near fully inflated, I pull the tire chuck off the valve stem, and instead, push the tire gauge onto the valve stem. It immediately shows me the pressure level in the tire. If I need to add more air I do, or if I have put in a bit too much air, I open the tire valve a bit (pushing down on metal button in the center of the valve stem) to bleed off air. Then I check the pressure again, until I have it set correctly.
A pressure regulator on the compressor may have a 2-5 PSI over or under range, so that’s why I like to check the tire pressure with a tire pressure gauge.