Guides · How to Check Tire Pressure
One Tire Keeps Losing Pressure
A single tire that needs air again and again is a leak until proven otherwise. Inspect the valve, tread, and bead.
Short answer
If only one tire drops, stop treating it as weather. Temperature usually moves all four. A repeat loser has a puncture, a leaking valve stem, a dirty bead, or a bent rim. Find the leak before the next highway trip.
Soap spray on the wet valve and around the bead will bubble on many leaks. A nail in the tread may only show after you rotate the tire and listen. Mark the spot. Do not pull a nail in a parking lot if you still have to drive; the object may be the only seal.
Valve stems age, especially on older TPMS sensors. A missing cap plus a wet stem is enough reason to replace the core or the stem. Caps are cheap. Sensors are not, but driving on a leaking sensor stem is worse.
Rim corrosion and curb hits cause bead leaks that look like 'slow winter loss' on one corner. A shop can dunk or scope the tire. You cannot fix that with a monthly top-off habit.
Use the calculator only to quantify the gap. It will not tell you why the same corner is always the one that changed.
Step-by-step
- 1Confirm the other tires are stable so this is not a weather event.
- 2Inspect the tread, sidewall, valve, and rim flange.
- 3Soap the valve and bead if you can do it safely.
- 4If you find a nail in the tread, decide on a repair shop, not another top-off.
- 5Replace a leaking stem or have the tire dismounted if the leak is at the bead.
Common mistakes
Monthly fill-and-forget A leak grows. The next failure can be fast.
Pulling the nail at the curb You may dump the remaining air.
Swapping just the valve cap and declaring victory Caps help, but a cracked stem still leaks.
Safety notes
A tire that goes from full to very low overnight is not a DIY highway experiment.
FAQ
Could it still be temperature? Only if the other tires moved about the same amount.
Is a plug in the sidewall OK? No. Sidewall damage is a replace, not a plug.