How a Portable Tire Inflator Works

They have motors and pistons inside, but no tank.

A person connects a tire inflator to the tire.
Depositphotos

There is no such thing as an opportune moment for a flat tire, only bad or worse times. It’s bad when you get a flat tire near your home and need to take the time to fill it up or fix it. It’s worse when it’s on the side of a busy highway. But the absolute worst time to get a flat is when you don’t have a temporary patch, your spare tire is also flat, and you’re nowhere near an air compressor. 

Unpreparedness creates more headaches, wastes more time, and costs more money. One way to ensure you always have, at the minimum, a fully inflated spare tire is to keep a portable tire inflator in your car. You can use it to keep your tires at the designated optimum pressure at any time, and you’ll have a backup plan for your spare tire just in case. 

A yellow tire inflator filling a tire off of its vehicle.
Depositphotos

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These devices go by many different generalized names, including tire inflator, mini air compressor, and portable air compressor, which can be confusing when considering many people think of air compressors as the large tanks that sit in the corner of a garage. So is it really an air compressor if it doesn’t have a tank? 

To clear up this confusion, the Guides & Gear team decided to “open up” a tire inflator and lay out all of its guts in an easy-to-understand explainer. Let’s begin.

Examining How a Tire Inflator Works 

Tire inflators are not the same as simple air pumps; they’re actually miniature air compressors. To better understand how they work, we’ve broken down the main components that make up these devices and explained how they work together to put air into your tires.

Wired or Wireless Power Source

The most common types of portable tire inflators will plug straight into a wall, plug into the 12V cigarette lighter in your car, or use battery power. Each has its own pros and cons, but the type that plugs into the 12V port is the most universal for drivers. 

Switch

The switch, whether in the form of a dial, slider, toggle, trigger, or a button, completes the device’s power circuit and turns the device on by engaging the motor. Essentially, the switch is how you turn the device on and off.

Electric Motor

The internal electric motor is the tire inflator’s powerhouse. The motor’s output shaft is primarily connected to gears that transfer the energy to the piston. In some cases, however, the output shaft is also connected to a fan that spins while the motor is running to cool down the device.

A blue tire inflator next to a wheel.
Depositphotos

Some tire inflators feature built-in handles.

Gears

In most tire inflators you’ll have two gears, one attached to the motor and one attached to the piston. When the motor moves, it turns its gear, which is inset with the piston’s gear. So, when the motor moves, the gears make the piston move. In some cases, there might also be a third gear to turn a fan. 

Piston and Cylinder

It’s not exactly the same, but your gas-powered vehicle does share a component type with a tire inflator: a piston. Although the motor drives the mechanism, the piston and the cylinder in which it is housed is where the action happens. 

As the gears turn, the piston is pulled down to bring air into the cylinder through an intake, then pushed up. When the piston goes up, the air is compressed and pushed through the tube that connects to the tire. The piston steadily repeats this cycle to continue compressing and pumping air into the tire.

Fan

Most tire inflators will be air-cooled by a small fan built into the device. The placement of the fan will vary, but it is likely next to or near the motor where a majority of the heat is created.

Valves

The piston wouldn’t be able to complete its purpose without valves working in tandem. The valve types, whether ball, flap, or other, will vary, but they all serve the same purpose: to get air into the cylinder when needed and prevent air from coming in when not needed.

Pressure Sensor

Your tire inflator might also use a pressure sensor. This can be used for reading the pressure to display it on a digital gauge, and/or they might be used to control a valve for automatic closing. 

Connector

The connector, or the tubing at the end of the tire inflator, is what pairs the inflator to the tire, ball, or whatever else needs inflating. It is typically made of rubber and is sometimes covered in a fabric wrap. Many new models offer a variety of tips that pair with the connector to allow for a variety of uses.

TL;DR

In short, you flip a switch, the motor turns on and drives a piston, which pressurizes and pumps air into your tire through the connector.

A black tire inflator with a yellow coiled hose connected to a BMW wheel and tire.
Depositphotos

Coiled hoses make storage easier.

So Is a Tire Inflator an Air Compressor? 

Technically, yes, a portable 12V tire inflator is an air compressor. However, it doesn’t have a tank to store compressed air, nor does it have the ability to power pneumatic tools. Therefore, it’s often referred to as a tire inflator or simply an inflator because that is the only specific job it is intended for and capable of.

FAQs About Tire Inflators and Air Compressors 

You’ve got questions, The Drive has answers!

Q. How long can tire inflators run? 

A. The motors inside tire inflators can heat up pretty quickly, and if the cooling isn’t adequate, they can’t run for very long. Some of the most common run times you’ll see are only for about 5-10 minutes, but each inflator will be different. Check the owner’s manual/service manual for specifics on your machine.

Q. Do tire inflators use oil? 

A. There are always exceptions, but a vast majority will not. Most tire inflators you encounter, especially if it’s new, are oilless.

Q. Can you use pneumatic tools with a tire inflator? 

A. To use pneumatic tools, you need an air compressor that can consistently produce high amounts of pressure and steady air flow for extended periods of time. Small tire inflators cannot accomplish any of these things, so they cannot power pneumatic tools.

Q. What size air compressor do I need to run pneumatic tools?

A. Different size air compressors are used for different tasks, so it depends on your goals, your budget, and the pneumatic tools you will be using. For more detailed information visit our guide,  how garage air compressors work and what size you’ll need, 

Q. How much should I fill my tires? 

A. This will be different for every vehicle and tire, so you’ll need to consult the information posted on the inside of your driver’s door or your owner’s manual. The tire itself will often show maximum tire pressure, but that’s not the same as recommended tire pressure.

Q. Can I trust the PSI gauge while the tire inflator is running?

A. First, if you are unaware, PSI stands for pounds per square inch and it’s a measurement of air pressure. When your inflator is plugged into your tire, it will register a PSI on the built-in gauge, if your device has one. But, those readings will be off while the tire is in the process of inflation. So, make sure you take your measurements while the inflator is turned off.

Learn More from This Video Teardown

Now that we’ve explained what a tire inflator does and how it works, we’d like to show you what the parts all look like. In the video below, the presenter takes apart a cordless Ryobi unit that has had some issues.

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