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Service · 6 min read

When to Replace Your Tires

Tread depth, age, and the wear patterns that mean something else is wrong.

Written and reviewed by Nicholas Velez, Founder, Car Dogs · Updated August 13, 2026

Quick answer

Replace at 4/32 of tread rather than waiting for 2/32, replace by age at six to ten years regardless of tread, and treat uneven wear as a suspension or alignment message.

Key takeaways

  • Penny test: insert Lincoln head down. If you see the top of his head, you're at 2/32 — replace now.
  • Find the DOT code on the sidewall; the last four digits are week and year of manufacture.
  • Both edges worn, center fine: chronic underinflation.
  • Match the size and load rating on your door jamb sticker, not just what's on the car now.
  • Check pressure monthly, when the tires are cold.

General information, not professional advice. Anything involving brakes, steering, tires, airbags, fuel or overheating should be inspected in person by a qualified technician before you drive on it.

Tires are the only part of your car that touches the road, and they're the single most common thing people drive on too long. Checking them takes two minutes and one coin.

Check tread depth in two minutes

New tires start around 10/32 of an inch of tread. The legal minimum in most states is 2/32, but wet-weather grip falls off badly well before that — plan replacement at 4/32.

  • Penny test: insert Lincoln head down. If you see the top of his head, you're at 2/32 — replace now.
  • Quarter test: if you see the top of Washington's head, you're near 4/32 — start shopping.
  • Find the molded wear bars in the grooves; flush with the tread means done.
  • Check inner and outer edges and both sides of the car, not just one spot.

Tires age out even with tread left

Rubber hardens and cracks over time regardless of mileage. Most manufacturers suggest replacement at six to ten years from the build date, whatever the tread looks like — which matters a lot for low-mileage drivers and spare tires.

  • Find the DOT code on the sidewall; the last four digits are week and year of manufacture.
  • Look for fine sidewall cracking, dry rot, or bulges — replace immediately on a bulge.
  • Full-size spares age too, and usually get forgotten.

What wear patterns are telling you

  • Both edges worn, center fine: chronic underinflation.
  • Center worn, edges fine: overinflation.
  • One edge only: alignment (camber or toe) needs correcting.
  • Patchy or cupped wear: worn shocks, struts, or an out-of-balance wheel.
  • Feathered edges across the tread: toe alignment.

How many to replace at once

Four is ideal, and on all-wheel drive it's often required — mismatched circumference can damage the drivetrain. If you replace two, they belong on the rear axle regardless of which wheels drive the car, because rear grip loss is much harder to recover from.

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Shopping without overpaying

  • Match the size and load rating on your door jamb sticker, not just what's on the car now.
  • Buy for your actual climate: all-season, all-weather, or a dedicated winter set.
  • Compare out-the-door pricing including mounting, balancing, valve stems and disposal.
  • Check treadwear warranty mileage — a cheaper tire that lasts half as long isn't cheaper.
  • Ask about road hazard coverage; wheel and tire protection is worth pricing separately too.

Make the new set last

  • Check pressure monthly, when the tires are cold.
  • Rotate every 5,000–7,500 miles, usually with your oil change.
  • Get an alignment when you install new tires, or after any hard pothole hit.
  • Balance the wheels if you feel vibration at highway speed.

Common questions

How do I know if my tires need replacing?
Use the quarter test: if you can see the top of Washington's head in the tread grooves, you're near 4/32 of an inch and should start shopping. Also replace any tire with a bulge, sidewall cracking, or a build date more than six to ten years old.
Do tires expire if I barely drive?
Yes. Rubber degrades with time and heat exposure, so a six-to-ten-year-old tire should be replaced even with plenty of tread remaining. Check the DOT date code on the sidewall.
Can I replace just one tire?
Sometimes on front- or rear-wheel drive, if the others are close to new and the same model. On all-wheel drive it's usually a bad idea — mismatched rolling circumference can damage the drivetrain.
Should new tires go on the front or rear?
The rear, when you're only buying two, even on a front-wheel drive car. Losing rear grip in the wet causes oversteer, which is much harder for a driver to correct.
Do I need an alignment with new tires?
It's strongly recommended. A small misalignment can ruin a new set in a few thousand miles, so an alignment is cheap protection for a much larger purchase.

The short version

Replace at 4/32 of tread rather than waiting for 2/32, replace by age at six to ten years regardless of tread, and treat uneven wear as a suspension or alignment message.

What should I do next?

  1. 1See what's actually due at your mileage
  2. 2Check for open recalls — that work is free
  3. 3Compare any quote against a fair range
  4. 4If something's wrong right now, start with Fix
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