The Penny Test and Beyond: How to Check Tire Tread Before a Northern Illinois Winter

Grab a penny, slip it upside down into a tread groove with Lincoln’s head pointing into the tire, and look. If you can see the top of his head, your tread is shallow and the tire needs a closer look. Next, check the wear bars and look for uneven wear across the tire. Then check pressure on a cold morning, because falling temperatures lower it. If the penny is close, the wear looks uneven, or you just aren’t sure, have a technician measure the tread before November weather settles in, and base any replacement on what that inspection finds. You can schedule service online with Woody Buick GMC of Gurnee any time.

November in Lake County can bring wet leaves, sleet and the first snow of the season within days of each other. Your tires are the only part of your vehicle that touches the road, and the tread is what helps provide traction when the pavement turns slick. Here’s how to do a tire tread check at home in Gurnee, and how to know when it’s time to hand the job to a pro.

The penny test takes about a minute and needs nothing but spare change.

Repeat the test at several points around each tire and across the inner, center and outer grooves. Tread rarely wears evenly, so one good reading doesn’t speak for the whole tire. Think of the penny test as a quick screen, not a precise measurement. It tells you whether a closer look is due.

Most tires have tread wear indicator bars molded into the bottom of the grooves, running across the tread. On many tires, the sidewall marks their location with a small triangle or the letters TWI.

On a newer tire, the bars sit well below the tread surface. As the tread wears down, the surface gets closer and closer to the bars. When the tread is flush with them, the tire has reached the end of its designed tread life.

Legal minimum tread depth is set by each state, so check your state’s requirement rather than relying on a rule of thumb. Keep in mind that a tire can still meet a minimum and offer less grip on wet or snowy roads than deeper tread.

Uneven wear is easy to miss and important to catch. A tire can pass the penny test in the center while its inside edge, the part you can’t easily see, is nearly smooth. Common patterns and what they often point to:

Uneven wear matters for two reasons. It shortens the useful life of the tire, and it’s often a clue that something else needs attention. Regular rotation on the schedule in your owner’s manual helps even out wear going forward, and a technician can read the pattern to find the cause.

Air contracts as it cools, so tire pressure falls along with the temperature. Tires set on a mild October afternoon can read low on a frosty November morning. That’s often why the tire pressure light comes on during the first cold week of the season, then goes off after a few miles of driving warm the tires back up.

A few habits help:

Running underinflated over a full season contributes to the edge wear described above, so pressure and tread go hand in hand. Cold mornings are hard on batteries too, so while you’re at it, read our post on battery warning signs before the first freeze.

Tread grooves give water, slush and snow a place to go so the rubber can stay in contact with the road. As tread wears down, those channels get shallower and can’t clear as much.

Wet leaves: matted leaves hold water against the pavement and can be surprisingly slick. Shallow tread has less ability to push through that layer, so stopping can take longer.

Slush: heavy, wet slush can lift a worn tire instead of letting it cut through, which can feel like the vehicle is floating or tugging.

The first snow: tread grooves and the small slits in the tread blocks provide biting edges. Worn tread has fewer and shallower edges to grip with.

Whatever the tread depth, wet leaves and slush call for more following distance and smoother steering and braking. Checking tread before the weather turns gives you time to act on what you find. Tires are one piece of getting ready, and our Beat the First Cold Snap fall maintenance checklist covers the rest.

The at-home checks are a great start, but some signs mean it’s time for a professional tire inspection in Lake County:

A technician can measure tread with a depth gauge at several points on each tire, inspect the sidewalls, check pressure and read the wear pattern for alignment or suspension clues. If you’re wondering when to replace tires in Illinois, that inspection is the answer. Replacement should be based on what it finds, not a guess. When you book a service appointment, ask our service department to measure your tread while your Buick or GMC is in. If it’s time for new tires, our parts center can help you find a set that fits, and it’s worth checking current service offers first.

Is the penny test accurate enough to decide whether I need new tires?
No. It’s a quick screen, not a precise measurement. It tells you whether tread is getting low and a closer look is due. A technician uses a tread depth gauge at several points on each tire, and any replacement decision should be based on that inspection.

Why does my tire pressure light come on when the weather turns cold?
Cold air contracts, so tire pressure drops as temperatures fall. The light often comes on during the first cold mornings and goes off after the tires warm up from driving. Check pressure before you drive against the number on the door jamb placard, and have the tire looked at if the light stays on or keeps coming back.

How low can my tread get before I need new tires?
It depends on your state’s requirement, so check what applies where you drive. When the tread is flush with the wear bars, the tire has reached the end of its designed tread life. Tread that still meets a minimum can offer less grip on wet leaves, slush and snow, so it’s worth having it measured before winter.

Can uneven tire wear be corrected?
The cause often can be fixed, but worn tread doesn’t grow back. Regular rotation helps even out wear going forward, and underinflation, alignment or suspension issues may need attention. A tire that has already worn unevenly may need replacement, based on what an inspection finds.

If the penny test was close or the wear looks uneven, let a technician take the measurement. Schedule service online and ask for a tire inspection. We’re at Woody Buick GMC of Gurnee, 5589 Northridge Drive, Gurnee, IL 60031, and you can contact us with any questions. Thinking about trading up before winter instead? Value your trade online.