If you’re about to inspect a used car, spend a few minutes on the tires— they directly affect braking, grip, and comfort, and their condition can also hint at how the car was maintained.
How to read the DOT code (tire age)
- DOT is a code on the sidewall that includes the production date. The last four digits show the week and year: for example, 2319 means the 23rd week of 2019.
- The code is sometimes facing inward; use a flashlight if needed. Check each tire individually— sets are often mixed in age or brand.
- Age is only part of the picture: tires that have sat for long periods or were exposed to sun and chemicals can harden and crack regardless of mileage.
Tread depth and safety margins
- Measuring: use a tread-depth gauge or a thin ruler marked in millimeters. Measure at least three places across the tread (inner edge, center, outer edge) and at several points around the circumference.
- What to look for: consistent depth without “plateaus” that are noticeably shallower than the rest.
- Safety margins (recommendations): it’s often advised to replace summer tires around 3 mm and winter tires around 4 mm, as shallower tread noticeably worsens wet and snow grip and raises the risk of aquaplaning. If the tread is near those values, plan the cost of replacement.
Uneven wear: what it tells you and what to check
- Inside or outside edge much more worn: possible misalignment (toe/camber) or worn suspension components.
- Center more worn than the edges: often too high tire pressure.
- Both edges more worn than the center: often too low tire pressure.
- “Cupping” or feathered tread blocks: may point to worn shock absorbers, wheel bearings, or a wheel-balancing issue.
- Vibrations while driving: check wheel balance and possible rim damage.
Quick on-the-spot checklist
- Sidewalls: look for bulges, cracks, cuts, and scuffs or “bites” from curb impacts.
- Tread: look for nails, screws, plugs from previous repairs, and any locally shallow areas.
- Valve stems and caps: cracked valves can cause slow air leaks.
- Set matching: same size and similar age on the same axle; unexpected mixes can indicate a stopgap replacement.
- Spare tire (if present): check pressure and condition— you might need it right after purchase.
In short, a thorough tire check helps you judge safety and future costs realistically. If the tires are old, unevenly worn, or close to the recommended safety margins, budget for a prompt replacement or use it in price negotiations. For more helpful tips before you buy, Browse all guides.