Frequently Asked Questions

TireSpy reads the last 4 digits of your tire's DOT code — a number stamped on every tire sidewall — and calculates the exact age of your tires. We then compare that age against safety thresholds recommended by NHTSA and tire manufacturers to give you a clear verdict.

Yes, completely free. No signup, no account, no data stored. Your DOT code never leaves your browser.

The age calculation is 100% accurate — it's a direct calculation from the manufacture date encoded in your DOT code. The safety thresholds are based on NHTSA guidelines and manufacturer recommendations, which vary slightly by brand.

Look on the sidewall of your tire — the flat face between the tread and the wheel rim. Find the letters "DOT" followed by a series of characters. The last 4 digits are the date code. Note: the full code is sometimes only on the inboard side (facing the vehicle).

A 3-digit code means your tire was manufactured before 2000. If that's the case, replace your tires immediately — they are dangerously old.

You may be looking at the wrong part of the code. The date code is always the very last 4 characters and always consists of numbers only. Look for a small oval or rectangle around these 4 digits.

Most manufacturers and NHTSA recommend replacing tires after 6 years regardless of tread depth. 10 years is the absolute maximum. TireSpy uses these thresholds adjusted for tire type — winter tires degrade faster and have slightly shorter safe limits.

Tire aging is not visible to the naked eye. Rubber hardens and loses elasticity at the molecular level long before cracks appear on the surface. A tire can look perfect and still have significantly reduced grip and blowout resistance. Age is as important as tread depth.

Yes. Winter tires use softer rubber compounds that degrade faster. All-season tires fall in between. Storage conditions also matter — heat, UV exposure, and ozone accelerate aging significantly.

We recommend Tire Rack, SimpleTire, and Discount Tire for US customers. See our full comparison on the Shop Tires page.

Yes — if you buy tires through links on our site we may earn a small commission at no extra cost to you. This is how we keep TireSpy free. We only recommend retailers we trust and our safety verdicts are completely independent of any commercial relationship.