When to Replace Tires
Written by Muneeb Rana · Last updated 21 October 2026
Quick answer: Replace tires when tread reaches 2/32 inch (1.6 mm), the US legal minimum in most states and the UK legal minimum across the central three-quarters of the tread, or sooner for wet and snowy roads. Also replace for bulges, cuts, exposed cords or age: NHTSA notes many manufacturers recommend replacement at 6 to 10 years regardless of tread.
TL;DR
- Minimum: 2/32 in (1.6 mm); replace sooner for wet grip.
- Penny test: see Lincoln's whole head, replace.
- Check the age: DOT date code; 6-10 years max.
Knowing when to replace tires is about three things: tread depth, damage and age. Here's how to check each in a few minutes.
Check tread depth
- Penny test (US): insert a penny head-first; if you can see all of Lincoln's head, tread is at or below 2/32 inch.
- Tread wear bars: raised bars across the grooves; when tread is flush with them, it's time.
- Gauge: inexpensive and precise.
The UK Highway Code requires at least 1.6 mm across the central three-quarters of the tread around the whole circumference; the fine can be up to £2,500 and 3 penalty points per tire.
Check for damage
Bulges or blisters on the sidewall, cuts, exposed cords, cracking, and uneven wear patterns. Uneven wear suggests an alignment, suspension or pressure problem (wheel alignment).
Check the age
The DOT code on the sidewall ends in four digits: week and year of manufacture (for example 2321 = week 23 of 2021). NHTSA says many vehicle manufacturers recommend replacing tires every six years regardless of tread, and many tire makers say 10 years maximum. Rubber ages even on a spare.
Make tires last
Keep pressure right (tire pressure guide), follow the tire rotation schedule, and fix alignment problems quickly. Fitting a different size? Use the tire size calculator. Log tire purchases and rotations in CarO to see real tire life, and watch for the tire pressure light.
Download CarO free on the App Store or Google Play. Free with ads; optional in-app purchases.
Sources
- NHTSA: Tire Safety (TireWise): www.nhtsa.gov (accessed 21 October 2026)
- GOV.UK: The Highway Code, Annex 6 (vehicle maintenance, safety and security): www.gov.uk (accessed 21 October 2026)
- Bridgestone: How to Read a Tire Sidewall: www.bridgestonetire.com (accessed 21 October 2026)
Disclaimer: CarO and this website give general car-care information, not professional advice. Maintenance intervals and specifications vary by vehicle, so always follow your owner's manual and a qualified mechanic. Mileage and cost figures are estimates; check local tax rules before using any log for deductions.
FAQ
What is the legal minimum tread depth?
2/32 inch in most US states, and 1.6 mm across the central three-quarters of the tread in the UK.
How do I do the penny test?
Put a penny into the tread with Lincoln's head upside down. If you can see all of his head, the tread is at or below 2/32 inch and the tire needs replacing.
How old is too old for tires?
Many vehicle makers recommend replacement at six years and many tire makers set 10 years as a maximum, according to NHTSA. Check the DOT date code.
How many miles do tires last?
It varies widely by tire, car and driving. Check the tire's treadwear warranty and measure tread regularly.
Should I replace all four tires at once?
Ideally in pairs or sets. AWD vehicles often need all four replaced together to keep diameters matched; check your manual.
Related guides
Track this in CarO
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