Your tire's size code contains everything you need to know about fit, load, and speed capability. Here's how to decode it — and find the right replacement.
A standard tire size looks like this: P215/65R16 98H. Each part tells you something specific: P = passenger vehicle, 215 = section width in mm, 65 = aspect ratio (sidewall height as % of width), R = radial construction, 16 = wheel diameter in inches, 98 = load index, H = speed rating.
The section width (215 in the example above) is the measurement from sidewall to sidewall in millimeters when mounted on the specified rim width. The aspect ratio (65) tells you how tall the sidewall is — a lower number means a shorter, sportier sidewall and typically a larger wheel diameter. Performance vehicles often run 35–45 series tires; trucks commonly use 75–85 series.
Common passenger sizes include 185/65R15, 195/65R15, 205/55R16, 215/60R16, 225/50R17, 235/45R18, and 245/40R19. Truck/SUV sizes commonly include 235/70R16, 245/70R17, 265/65R18, and 275/55R20. Always verify against the vehicle's door placard before purchasing.
Minor upsizing (plus-sizing) is common — going up one inch in wheel diameter while reducing the aspect ratio to maintain the same overall diameter. This keeps the speedometer accurate and maintains handling balance. Significant changes require professional consultation to avoid rubbing, clearance issues, and speedometer error.
