How to Inspect Tires Before a Road Trip: Checklist

Why a pre-trip tire inspection matters

The hours of highway driving on a road trip put steady stress on your tires. Heat builds up, loads are constant, and a defect that would never surface during a short commute can turn into a failure at speed. A 10-minute inspection before you leave covers the three areas that cause the majority of tire problems: tire pressure, tread, and visible damage.

Proper inflation also affects your fuel budget. The U.S. Department of Energy reports that keeping tires inflated to the recommended pressure can improve gas mileage by 0.6 percent on average, and under-inflated tires can lower gas mileage by about 0.2 percent for every 1 psi drop in the average pressure of all tires. That means even a few psi of under-inflation can add up over a long drive.

Check tire pressure

Start with the pressure. Use a good tire gauge and check each tire when the tires are cold. Cold means the vehicle has not been driven for a few hours, so the air inside has stabilized. The recommended cold inflation pressure for your vehicle is printed on a placard on the driver's side door jamb, on the glove box, or in the owner's manual. Do not use the maximum pressure number molded on the tire sidewall; that is the tire's maximum permissible inflation pressure, not the vehicle's recommendation.

The federal standard for tire pressure monitoring systems requires the warning light to come on when a tire's pressure falls to 25 percent or more below the vehicle's recommended cold inflation pressure. That means the TPMS will not alert you to moderate under-inflation. A manual check with a gauge catches tires that are only a few psi under spec.

If a tire reads low, add air to reach the recommended pressure. Recheck each tire after adding. If a tire loses pressure again quickly, find the cause before you leave. A nail or a damaged valve stem can cause a slow leak that will leave you stranded.

• Check tires when they are cold.
• Read the recommended pressure from the vehicle placard.
• Remove the valve cap and press the gauge firmly onto the stem.
• Note the reading and adjust with an air pump.
• Replace the valve cap.

Check tread depth

Tread depth is what lets your tires evacuate water and grip the road. Every tire has tread wear indicators, which are small raised bars molded into the bottom of the main grooves. Federal regulations describe these indicators as designed to give a visual indication of the degree of wear of the tread. When the surrounding tread is worn down to the level of these bars, the tire has reached the point where it should be replaced.

To check, look at each groove on the tire. If any indicator is flush with the tread surface, the tire is worn out and you should not drive on it, especially for a highway trip. Many drivers also use a tread depth gauge for a precise measurement, but the indicators are the quickest method and require no tools.

Uneven wear across the tire can indicate an alignment, inflation, or suspension issue. If you see one shoulder worn more than the other, or a bald strip in the center, the tire may not be safe even if the indicators in other grooves are still above level. In that case, have the vehicle checked and consider replacing the tire.

Look for visible damage

Inspect the sidewalls and tread for damage that could fail on the road. Federal standards define several types of damage. Cracking is any parting within the tread, sidewall, or innerliner that extends to cord material. Chunking is the breaking away of pieces of the tread or sidewall. Tread separation, sidewall separation, and ply separation are all breakdowns of the tire's internal structure.

Run your hands over the sidewalls and tread. Feel for bulges, which indicate internal belt or cord damage, and for cuts or tears. Look for embedded objects like nails, screws, or stones that have pierced the rubber. If you see any cord fabric, steel belts, or wire through a cut, the tire is not repairable and must be replaced.

Also check for cracking on the sidewall, which can happen with age. Small surface cracks are common, but cracks that are deep enough to expose cords are a serious problem. In the same way, inspect the bead area where the tire meets the rim for damage or air leaks. A leak at the bead may require the tire to be remounted.

• Cuts or tears in sidewall
• Bulges or bubbles
• Embedded nails or objects
• Cracks exposing cords
• Uneven wear patterns

Don't forget the spare tire

If your vehicle carries a spare tire, it needs the same checks. Spare tires are often underinflated because they sit unused for long periods. Check the air pressure using the cold pressure specification from the owner's manual or the placard for the spare. Also inspect the spare for cracks, bulges, or damage from age. A full-size spare should meet the same specifications as your road tires, while a compact temporary spare has different pressure and speed limits.

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Questions

How often should I check my tire pressure before a road trip?

Check pressure at least once before a long trip, and ideally once a month. The TPMS only warns at 25 percent below recommended, so manual checks catch moderate drops.

Can I repair a tire with a nail in the tread?

If the nail is in the repairable area of the tread and the tire has not been driven flat, a professional patch can often repair it. Do not attempt a repair yourself if the damage is near the sidewall.

What is the minimum tread depth for highway driving?

The wear indicators are set so that when they are flush with the tread, the tire has reached the legal minimum. For safer wet traction, many drivers replace before that point.

What does a bulge in the sidewall mean?

A bulge indicates internal belt separation. The tire is unsafe to drive on and must be replaced immediately, not repaired.

Should I check the spare tire before a trip?

Yes, spares often sit uninflated. Check pressure according to the owner's manual and inspect for damage. A compact spare has a lower pressure rating and a maximum speed limit.