Tire pressure is one of the most commonly neglected maintenance items, and one of the most impactful. It affects how your car handles, how fast your tires wear, how much fuel you use, and whether a blowout is more or less likely at highway speed.
What the right pressure actually does
Tires are designed to make a specific contact patch with the road — a footprint. When the tire is at the correct pressure, that footprint is the right shape and distributes load evenly. When it's underinflated, the tire bows outward, and the edges contact more than the center. When overinflated, only the center contacts the road. Both cause uneven wear and compromise handling.
The right pressure for your car
Here's a common mistake: people look at the number molded into the tire sidewall and assume that's the correct pressure. It's not — that's the maximum pressure the tire can handle. Your correct inflation pressure is on a sticker on the driver’s-side door jamb, and it's often different front and rear.
How quickly pressure changes
Tires naturally lose about 1 PSI per month under normal conditions. Temperature changes have a significant effect — about 1 PSI per 10°F. That means a tire properly inflated in October at 72°F may be down 4–5 PSI by January when it's 20°F. In Chicago winters, checking pressure in the fall and again in midwinter is good practice.
TPMS — what it does and doesn't do
Most vehicles made after 2007 have a Tire Pressure Monitoring System that alerts you when a tire drops significantly below the correct pressure. But TPMS typically doesn't trigger until pressure drops by 25% below recommended — which means you can be meaningfully underinflated without a warning light. Don't rely solely on the TPMS light as your inflation check.
How to check your pressure
Get an inexpensive tire pressure gauge — digital or dial — and check each tire when the tires are "cold" (before you've driven more than a mile or two). Remove the valve cap, press the gauge onto the valve stem, and read the pressure. Compare to your door jamb specification. If it's low, add air.
We check and adjust tire pressure on every vehicle that comes into ProAuto, regardless of what service you're in for.
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