How to Read a Tire Sidewall

Start with the size, not the brand

A common passenger marking such as 225/65R17 identifies nominal section width in millimeters, aspect ratio, radial construction, and wheel diameter. It does not by itself prove that the tire fits every vehicle currently using a 17-inch wheel. Compare the complete marking with the vehicle placard, current approved fitment, and manufacturer guidance. LT, ST, flotation, and commercial formats follow different conventions. Record the marking exactly in a listing or quote request, including any prefix, suffix, load range, and service description.

Read the service description

The load index and speed symbol normally follow the size. The load index maps to a maximum carrying capacity at specified conditions, while the speed symbol identifies a standardized performance category. Do not substitute a lower rating merely because the dimensions match. Vehicles with staggered fitments, reinforced or extra-load tires, commercial duty, towing, or high curb weight need particular care. A seller should photograph this area clearly, and a buyer should confirm that the rating is appropriate for the exact axle and vehicle.

Find the DOT tire identification number

The DOT tire identification number contains plant and production information. The final four digits, when present in the familiar modern format, identify production week and year. Age is one inspection input, not a complete condition verdict. Storage, heat, underinflation, overload, repairs, impact damage, and ozone exposure also matter. Photograph the full code on each tire because the complete number may appear on only one sidewall. Ask the tire or vehicle manufacturer for age-related replacement guidance rather than relying on a marketplace shortcut.

Understand construction and certification markings

Sidewalls may identify radial construction, tubeless design, maximum load and pressure, materials, traction and temperature grades, severe-snow markings, mud-and-snow labels, original-equipment codes, run-flat systems, or electric-vehicle-related branding. These labels answer different questions and are not interchangeable. For example, an M+S label is not the same evidence as the three-peak mountain snowflake marking. A maximum pressure marking is also not a universal daily inflation recommendation; normal vehicle pressure comes from the vehicle placard unless authoritative guidance says otherwise.

Inspect the physical sidewall

Text is only half of the inspection. Look for cuts, cracks, bulges, exposed cords, bead damage, abrasion, weathering, suspicious repairs, and distortion. Compare all tires in a set for matching size, service description, construction, tread pattern, and similar wear. Used-tire buyers should request tread-depth readings at several points and images of both sidewalls, the tread face, bead, and DOT code. If damage or fitment is uncertain, stop and have the tire inspected by a qualified tire professional before installation.

Build a complete listing or RFQ

A useful TireAds record includes brand, model, complete size, load index, speed rating, load range where applicable, quantity, condition, measured tread depth, DOT week and year when known, repair history, price basis, location, fulfillment, and clear photos. Buyers should add vehicle year, make, model, trim, wheel size, use case, ZIP code, and installation needs. Those facts reduce mismatches and make seller responses easier to compare.

Sources and further reading

These primary and authoritative resources support the manual's research. Always use the current vehicle, tire, manufacturer, and regulatory guidance for a specific decision.

• Tire Safety Ratings and Awareness (TireWise)National Highway Traffic Safety Administration