Hot-weather tire care: pressure, tread and blowout risk

Tires are the only part of your car that touches the road, and they work hardest in summer. Hot pavement, long trips and heavy loads all push rubber closer to its limits. Most summer tire failures are not sudden surprises. They are the end of a slow problem that a quick check could have caught.

What heat does to a tire

Air expands as it warms. A tire's pressure typically rises by about 1 psi for every 10°F increase in temperature, and driving adds more heat through friction and flexing. Pavement on a sunny day can be far hotter than the air above it. A tire that starts out under-inflated flexes more, generates more heat and wears faster, which is the combination that most often leads to a blowout.

Over-inflation causes problems too. A tire that is too firm has a smaller contact patch, grips less, wears down the center of the tread and takes impacts harder.

Check pressure the right way

1. Check pressure when the tires are cold, meaning the car has sat for at least three hours or been driven less than a mile.
2. Use the pressure printed on the sticker inside the driver's door jamb, not the maximum number molded on the tire sidewall.
3. Use a reliable gauge. Built-in gas station gauges are often inaccurate, so keep a pocket gauge in the glove box.
4. Do not let air out of a hot tire to "fix" a high reading. Hot pressure naturally runs higher and will settle once the tire cools.
5. Check the spare as well. A flat spare is no help on the side of the road.

Check at least once a month, and before any long trip. If a tire loses more than a couple of psi in a few days, there is probably a slow leak that needs finding.

Tip: If your car has a tire pressure warning light, treat it as a final alert, not a monthly reminder. The light usually comes on only after pressure has dropped by around 25 percent.

Inspect the tread

Tread channels water away and give the tire grip. Summer storms can make hot roads slick, so worn tread is a risk even when the sun is shining.

• Depth: New tires typically have about 10/32 inch of tread. Most experts recommend replacing at 4/32 inch for wet-road safety, and the legal minimum is 2/32 inch. A simple depth gauge is inexpensive and easy to use.
• Wear patterns: Wear on both shoulders usually means under-inflation. Wear down the center suggests over-inflation. One-sided wear points to an alignment issue.
• Wear bars: Small raised bars in the tread grooves become level with the surface as the tire wears out.

Look for damage

Walk around the car once a month and look closely at each tire, including the inner sidewall if you can see it. Warning signs include:

• Cracks, cuts or small splits in the sidewall, often caused by age and sun exposure
• Bulges or blisters, which mean the internal structure is damaged and the tire should be replaced right away
• Nails, screws or stones lodged in the tread
• Vibration at highway speeds, which may point to a balance problem or internal damage

Tires also age. Rubber hardens over time even if the tread looks fine, so ask for a check once a tire is about six years old. The four-digit date code on the sidewall shows the week and year it was made.

Load, speed and long trips

Heavier loads need correct inflation. Check the door jamb sticker or owner's manual for guidance when towing or carrying a full car. Sustained high speed raises tire temperature quickly, so slow down on long, hot highway stretches and take breaks. Rotating tires on the schedule in your manual helps every tire wear at an even rate.

Before you leave on a summer trip

1. Set all four tire pressures cold, and check the spare.
2. Measure the tread depth on every tire.
3. Inspect the sidewalls for cracks, bulges and embedded objects.
4. Make sure your jack, lug wrench and locking wheel nut key are in the car.
5. Have an alignment check if you have noticed pulling or uneven wear.

When to get help

If you find a bulge, a deep cut, or tread near the wear bars, replace the tire rather than gambling on a few more weeks. Our team at Northline checks tire condition as part of every maintenance visit, and you can always ask us to look at yours.