Check tire wear with the penny test or a tread depth gauge
The penny test is the fastest way to check if your tires are worn down. Insert a penny into the tread grooves with Lincoln's head upside down and pointing into the tire. If you can see the top of Lincoln's head, your tread is too shallow and the tire needs replacement. If the tread covers part of his head, you still have usable tread left.
A tread depth gauge gives you a precise measurement. These cost $5 to $15 at auto parts stores and hardware stores. Press the gauge into the tread at several spots around the tire — the center, the sides, and between the ribs. Most tires are considered worn out at 2/32 of an inch of tread depth, though many safety experts recommend replacing them at 4/32 of an inch, especially if you drive in wet conditions often.
Check all four tires, not just one. Wear patterns vary depending on alignment, inflation pressure, and driving habits. A tire that looks fine on one side of the vehicle may be nearly bald on the other.
Key Takeaways
- The penny test tells you in seconds whether tread is dangerously low — insert a penny upside down and see if the top of Lincoln's head is visible.
- A tread depth gauge measures in 32nds of an inch and costs under $20; most tires should be replaced at 2/32 inch, though 4/32 inch is safer in rain.
- Uneven wear across the tire or between tires signals alignment problems or pressure issues that need attention before replacement.
- Check all four tires regularly, especially before long drives or winter weather, because wear patterns differ across the vehicle.
Look for uneven wear patterns that signal other problems
Tires do not always wear evenly, and the pattern tells you something is wrong with the vehicle itself. Center wear — the middle of the tire wearing faster than the edges — usually means overinflation. Check your tire pressure against the number on the driver's door jamb (not the maximum pressure on the tire sidewall), and adjust if needed.
Edge wear — both outer edges wearing faster than the center — typically points to underinflation or a suspension problem. Low pressure makes the tire flex more at the edges, causing faster wear. Overloading the vehicle can also cause this pattern.
One-sided wear — one edge wearing much faster than the rest — usually means your wheels are out of alignment. This is common after hitting a pothole or curb. Alignment problems get worse over time and will destroy a new tire quickly, so have the alignment checked before buying replacements.
Cupping or scalloping — a wavy pattern around the tire edge — suggests suspension wear or loose components. This creates a thumping sound as you drive and needs a mechanic's inspection.
Measure tread depth at multiple spots on each tire
Tread does not wear uniformly across the tire surface. The center may be thicker than the edges, or one side may be thinner than the other. To get an accurate picture, measure at least three spots on each tire: the center, the inner edge, and the outer edge.
If you are using a tread depth gauge, press it straight down into the groove until it stops. Read the number on the gauge. Repeat this at different points around the tire, rotating around the circumference. Write down the lowest reading — that is the measurement that matters for safety.
If you are using the penny test, repeat it in several grooves around the tire. If any spot shows the top of Lincoln's head, the tire is worn enough to replace, even if other spots still have tread. One thin spot is enough to compromise traction.
Know the difference between legal and safe tread depth
The legal minimum tread depth in most places is 2/32 of an inch. At this depth, a tire still technically functions, and you will not fail a safety inspection. However, this is the bare minimum — it is not the same as safe.
At 2/32 inch, wet traction drops significantly. Stopping distance increases, especially on wet roads. Many safety organizations, including the National Highway Traffic Safety Administration, recommend replacing tires at 4/32 of an inch if you drive in rain or snow regularly. At 4/32 inch, you have roughly twice the wet braking performance compared to 2/32 inch.
If you live in an area with frequent rain or winter weather, use 4/32 inch as your replacement threshold. If you drive mostly on dry roads, 2/32 inch is the legal floor, but replacing closer to 4/32 inch is still safer.
Check tire pressure while you are checking tread
Tire pressure affects both wear patterns and how accurately you can assess tread depth. Underinflated tires flex more, which can make tread look thinner than it actually is in the center. Overinflated tires wear the center faster and may give a false sense of remaining tread at the edges.
Check pressure when the tires are cold — before you have driven the vehicle or at least three hours after driving. Pressure increases as tires heat up from friction, so a warm-tire reading will be higher than the actual resting pressure. Find the correct pressure on a sticker inside the driver's door jamb, not on the tire sidewall. The sidewall shows the maximum pressure the tire can safely hold, not the pressure your vehicle needs.
Use a tire pressure gauge (digital or dial type, both cost under $15) or the air pump at a gas station, which usually has a built-in gauge. If pressure is low, add air. If it is high, let some out. Correct pressure improves fuel economy, extends tire life, and gives you a more accurate tread reading.
Replace tires before they reach minimum depth if you see warning signs
Tread depth is not the only reason to replace a tire early. Cracks in the sidewall, bulges, or visible damage mean the tire structure is compromised and replacement cannot wait. A bulge indicates the internal layers are separating, and the tire can fail suddenly at highway speed.
Vibration or thumping while driving, especially if it gets worse over a few days, can signal cupping, a flat spot, or internal damage. These problems usually require replacement rather than repair. Pulling to one side while braking may indicate uneven wear or damage on one tire.
If a tire has been patched before and is now leaking again, or if the puncture is larger than 1/4 inch in diameter, replacement is safer than another patch. Patches are temporary fixes and work best on small punctures in the tread area, not on sidewalls or near the edge.
Keep a record of when you last checked and rotated your tires
Tire wear accelerates over time, so checking once is not enough. Check tread depth every month or before long trips. Keeping a straightforward record — even just a note on your phone — helps you spot whether wear is speeding up, which can indicate pressure problems or alignment issues.
Tire rotation every 5,000 to 7,000 miles slows wear and helps catch problems early. During rotation, a technician moves tires to different positions on the vehicle, which evens out wear patterns. This extends the life of all four tires and gives you more time before replacement becomes necessary.
If you notice wear accelerating between checks, or if tread depth drops noticeably in just a few weeks, have the alignment and suspension inspected. Rapid wear usually signals a fixable problem that will destroy a new tire just as quickly if left alone.
Frequently Asked Questions
How often should I check my tire tread?
Check tread depth at least once a month and before any long drive. If you notice uneven wear or suspect a problem, check more often. Seasonal changes — especially before winter — are a good time to inspect all four tires.
Can I use a coin other than a penny for the penny test?
A penny works because Lincoln's head is at a specific height from the edge. A quarter also works — if the tread covers Washington's head, you have at least 4/32 inch. A dime works for checking the 2/32 inch minimum. Pennies are easiest because they are common and the measurement is well-known.
What if one tire is worn but the others are fine?
If one tire is significantly more worn than the others, have the alignment and suspension checked before replacing just that tire. Uneven wear usually means something else is wrong. Replacing one tire when the others are fine can also cause handling problems, so most shops recommend replacing at least two tires at a time, in matching pairs on the same axle.
Does tire age matter even if tread looks okay?
Yes. Tires degrade over time regardless of use. Most manufacturers recommend replacing tires after six years and definitely by ten years, even if tread depth is acceptable. Check the sidewall for the tire's manufacture date — it is a four-digit code showing the week and year made.
What should I do if I find a nail or puncture?
Do not remove the object. Drive slowly to a tire shop. Small punctures in the tread (under 1/4 inch) can sometimes be patched, but sidewall punctures cannot be safely repaired. The shop will assess whether patching is safe or if replacement is necessary.