As the only contact point between your vehicle and the road, tires are responsible for translating every decision you make behind the wheel. Suspensions, engine mods, and styling upgrades tend to steal the spotlight, but it’s the tires that are on the front line during every commute. If they fail, none of the other parts really matter. Not even the brakes.
That means, drivers should understand how tires function and do their best to keep them in check. You don’t need a master’s in tire theory, but you should know the basics—starting with tire pressure.
It may seem simple, but tire pressure is a big factor in both performance and longevity. More importantly, it changes with the seasons as temperatures rise and fall. Staying on top of it matters. So keep reading, and we’ll show you how.
Why Tire Pressure Matters
In the simplest terms, tire pressure affects how well a tire grips the road and how evenly it wears over time. The air inside your tires needs to be at the right level so the tread can make proper contact with the pavement. When it does, you get better traction and the tire wears evenly. Too much or too little air can reduce grip and cause uneven wear.
Keeping tire pressure in check gives your tires the best chance to perform well and live a long service life. But it’s not something you can just set once and then forget about until you need a new set of rubber. Tire pressure fluctuates with temperature, so you need to check it regularly and adjust as needed.
Pro Tip: Always follow the tire pressure specs in your vehicle owner’s manual or on the door jamb. The number printed on the tire’s sidewall is the maximum it can safely hold—not the pressure you should aim for.
Understanding Cold Tire Pressure vs Hot Tire Pressure
Most things expand and contract as temperatures change, and your tires are no exception. As a tire heats up, the air inside expands, increasing the tire’s pressure; as it cools, the air contracts, lowering the pressure.
Tire pressure is measured in pounds per square inch (PSI)—the amount of force the air inside the tire exerts on each square inch of its inner surface. As a general rule, for every 10°F change in temperature, tire pressure will increase or decrease by about 1–2 PSI. That means a chilly morning can cause your tires to lose pressure, while a hot afternoon or a long drive can make it rise.
Because of these fluctuations, it’s important to check and adjust tire pressure as the seasons change. A drop in ambient temperature in the fall or winter can leave properly-inflated tires slightly underinflated and at risk of uneven wear. Tire pressure can also rise during driving as the tires heat up from friction. That’s why manufacturers recommend checking pressure when the tires are “cold”—before you’ve driven or after the car has been parked for several hours. Cold tires give a more accurate and stable reading, so you can inflate them to the correct level.
How to Take Tire Pressure
Checking and adjusting tire pressure is a very quick and simple car maintenance procedure. It’s even easier if your vehicle has an onboard Tire Pressure Monitoring System (TPMS), which provides real-time readings on the dashboard. Older vehicles may not have this feature, so you’ll need a tire pressure gauge to verify pressure manually. Gauges can be analog (pencil-style or dial) or digital, but they all work on the same principle.
When checking pressure manually, always start with cold tires. Then follow these steps:
- Remove the small cap covering the valve stem.
- Attach your tire pressure gauge to the valve stem, pressing down on the Schrader valve to let air into the gauge.
- Compare the reading to the recommended pressure in your vehicle’s owner’s manual or on the door jamb.
If your tire’s pressure is off, you’ll need to adjust it.
- To let air out, use the gauge to depress the Schrader valve in the valve stem, monitoring the numbers until the pressure reaches the correct level. Many gauges have a small built-in tool to make this easier.
-
To add air, use an air compressor, tire filling station, or portable inflator. Some digital gauges include an inflator that automatically stops filling once the tire reaches the correct pressure. Traditional “analog” inflators require you to periodically check the gauge as you fill to avoid overinflating.
Tire Warning Signs Beyond Pressure
When tire pressure moves outside the normal range, the signs are usually easy to spot. With underinflated tires, you may notice vibrations and poor traction as you drive. In some cases, the tire may actually look like it’s sagging. Overinflated tires—which can be very dangerous—may feel stiff or bouncy and sometimes look rounder than usual. To help drivers notice any issues, most modern vehicles have built-in TPMS sensors that throw an alert on the dashboard when pressure is off.
However, pressure fluctuations aren't the only thing to look out for when monitoring tire health. Keep an eye out for these other warning signs that can indicate your tires need attention—or that something else in the vehicle requires service.
- Dry Rot: Rubber breaks down with age and exposure, causing cracks to appear across the tire’s surface. Cracked tires are sign a tire has reached the end of its service life and needs to be replaced. Most tires last five to seven years before this becomes an issue.
-
Vibrations at Speed: Wheel and tire assemblies must be balanced to function properly. If you feel vibrations at higher speeds, the weights may have shifted or the tire may have worn to the point where the old balance spec is no longer accurate. A shop can rebalance the assembly as needed.
- Uneven Wear Patterns: When tires are properly inflated, the tread should wear evenly across the tire. Uneven wear is a clear sign that something is wrong. Thankfully, the nature of the wear pattern can provide clues as to what the problem is, such as alignment, pressure, or suspension issues.
- Flat Spots: Tires that sit in the same position for a long time may develop flat spots, causing a rumble to occur while driving. Some flat spots work themselves out after driving, however most require replacement.
-
Tread Depth: Tire tread gradually wears down over time, reducing a tire’s grip and performance. When the depth reaches reach less than 4/32-inch in, you should replace the tires, with 2/32-inch being the absolute minimum. A tread depth gauge can help you monitor this degradation, but if you don’t have one, grab a penny. Insert the coin in between the tire tread blocks, with Lincoln’s head facing down. If the top of his head is visible, it’s time to replace the tire.
Get the Right Tires, Hassle-Free
While regular monitoring and maintenance are key to performance, longevity, and safe travel, choosing the right tires for your environment is just as important. After all, no amount of maintenance can make a tire suitable for conditions it wasn’t designed to handle.
Whatever your tire needs, Parts Via has you covered. We stock a full range of tires and tire care products from the top brands you know and trust, and our customer service team is ready to answer your questions. We can even ship tires directly to the installer of your choice free of charge—just select the “ship to store” option at checkout and get back on the road safely and quickly.