How to Fill Your Tires With a Portable Inflator
3 lessons in this series, 7 min in total
- What PSI Should Your Tires Be? Read the Door-Jamb Label 3 min read
- When Does the Tire Pressure Light Come On? 2 min read
- How to Fill Your Tires With a Portable Inflator 2 min read
The steps follow Continental’s tire-pressure guide and the user manuals for the Fanttik X8 Apex and AstroAI CZK-3674 inflators. See how we research.
Before you start
Your target is the cold pressure on the car’s tire placard, the label usually on the driver’s door jamb. It can differ between front and rear axles, so note both. If you haven’t found yours yet, start with what PSI your tires should be.
Fill while the tires are cold. Continental counts tires as cold when the car has been parked for 3 hours or more, or driven less than a mile (1.6 km).
Check the units too. The Fanttik X8 Apex manual warns that mixing up psi and bar could lead to dangerous overinflation, so make sure the display shows the same unit as your placard.
Step by step
- Get the target. Read the cold PSI for the front and rear tires from the placard.
- Start cold, ideally before the first drive of the day.
- Remove the valve cap and set it somewhere safe.
- Connect firmly. Press the connector onto the valve stem until the hissing stops, as Continental advises for a gauge.
- Set the target. On the Fanttik X8 Apex, pick a mode, set the pressure with + and -, then press power. On the AstroAI CZK-3674, set it with + and -; its switch doesn’t reset after auto shut-off, so switch it off by hand.
- Fix any overshoot. Release a little air and recheck; to learn your unit’s offset, see how to check your inflator against a reference gauge.
- Disconnect quickly. The Fanttik manual says this limits air loss, and warns the hose can get very hot.
- Repeat on every tire and the spare, then put the caps back on.
If the dashboard light stays on after every tire is at its placard number, read when the tire pressure light comes on.
Which inflator suits this job
The AstroAI CZK-3674 is rated to 100 PSI (6.9 bar) and the Fanttik X8 Apex to 150 PSI (10.3 bar), both above the 60 PSI (4.1 bar) a 2025 Kia manual lists for its compact spare. So either one can fill a donut spare, and the real choice is the power source: the AstroAI runs from the car’s 12V socket, the Fanttik from its built-in battery. The trade-offs are laid out in cordless vs 12V tire inflators.
To decide what else should ride in the trunk with your inflator, work through the roadside emergency kit checklist.
