Making Air...

Compressors are the source of air, so if you don't have one, you don't have air. You would have to stop at a gas station and fill up your airtank every time you're out. For a simple install why not get a compressor. Here's a diagram giving you a basic idea of what you have to take on.

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You should go to various online forums to find what relay you would need for your specific application. Your setup might also differ from the one shown here.

This is not the only type of compressor you can get. There are some belt driven compressors that require you to mount inside the engine compartment, attached to the drivebelt system. These compressor blow massive amounts of air compared to a regular electric one, but the installation might not be a pleasant one. Either way you will be able to replenish you air. Different compressors have different duty cycles. Some have 100% duty cycle, meaning they can flow air all of the time. You can fill 100 tanks without it kicking off. Others are 20%, they can run 12 minutes out of the hour, so it might take a little longer to fill your tank if you have a high demand (hitting the switches constantly). So basically if you have a low duty cycle compressor then make sure you don't run out of air before you take on that speed bump. A good place to mount it is near the tank with a check valve on the line between them. A check valve makes sure the pressure from the tank isn't making a force directed towards the compressor. You should use this because filling a tank isn't like filling a tire. Tanks hold anywhere from 120psi to 250psi and even more. It exerts much more outwards force than a tire. All in all, it's nice to have a compressor on board to save you from trips to the pumps.