The Penny Test and Four Other Things Your Tires Tell You Before They Fail

Most tire failures aren't sudden. A tire that blows out on I-70 usually spent weeks or months telling you something was wrong. The trouble is most people don't know what to look for, so the warning goes unread until it's a flat on the shoulder or worse. Here are five things you can check in the time it takes to walk around your own car.

1. The penny test

This is the one most people have heard of and the one most people do wrong. Take a penny, Lincoln's head facing you, and push it into a tread groove. If any part of his head is covered by rubber, you've got tread left. If his whole head is visible, you're at or below 2/32 of an inch, which is the legal minimum in most states and honestly past where you want to be riding on wet roads. Do this in at least three spots across each tire, not just one. Tires wear unevenly, and a tire that looks fine in the middle can be bald on the outer edge.

2. Uneven wear patterns

Run your palm across the tread, not just your eyes across it. Wear on the outer edges usually points to underinflation. Wear concentrated in the center usually means overinflation. Wear on just one edge, or a choppy, feathered pattern you can feel with your hand but can't quite see, is often alignment. None of these are things you should just top off and forget. If you're feeling an edge that's noticeably lower than the rest of the tire, that's worth a look before your next rotation, not at your next rotation.

3. Bulges, bubbles, and sidewall damage

A bulge or bubble on the sidewall means the internal structure of the tire, the cords that actually hold air pressure, has been damaged, usually from hitting a pothole or curb hard enough to pinch the tire against the wheel. This is not a slow-leak problem, it's a structural one, and it can let go without warning at highway speed. If you see a bulge, don't drive on it. Get it looked at the same day if you can.

4. Vibration through the steering wheel

A vibration that shows up around 50 to 60 mph and gets worse the faster you go is a classic sign of a balance problem, or in some cases a belt starting to separate inside the tire itself. It's easy to get used to a vibration and just tune it out, but tires don't fix themselves, and a belt separation left alone eventually turns into a tread chunk coming loose at speed.

5. The date on the sidewall

Every tire has a four digit code stamped into the sidewall, usually after the letters DOT. The first two digits are the week, the last two are the year. A tire that's six or seven years old can look fine on the outside and still have rubber that's dried out and lost flexibility underneath, especially if it's spent summers sitting in a driveway. Tread depth isn't the only clock running on a tire.

Don't forget the spare

The tire most people never check is the one they never drive on. A spare tire that's sat under the trunk floor for years can be just as dry and cracked as an old tire that's been on the road the whole time, and it's easy to find that out at the worst possible moment, on the shoulder, in the dark, with the tire you actually need to replace already flat. Pull the spare out once or twice a year and check its pressure and its date code the same way you'd check any other tire. A spare that's flat or dry rotted isn't a spare, it's just extra weight in the trunk.

How often to actually look

You don't need to do a full inspection every week. A quick glance and a pressure check once a month, plus a real hands-on look whenever you get your oil changed or your tires rotated, is enough to catch most of this early. The point isn't to become paranoid about your tires, it's to notice the small things before they become big things. A tire that's slowly wearing unevenly gives you months of warning. A tire that's about to blow usually gives you weeks, sometimes less.

None of these checks take more than a few minutes, and doing them a couple times a year is cheap insurance against a bad afternoon on the shoulder of I-70 or I-635. If you find something that doesn't look right, we'll take a look at no charge and give you a straight answer, not a sales pitch. Boulevard Tire & Service has been doing this on Southwest Blvd in Kansas City, KS since 1994, and we carry Michelin, Bridgestone, Goodyear, Cooper, and most other major brands, usually in stock the same day. Call us at (913) 262-0111 if something feels off, we'd rather look at it now than read about it later.