175/65R14 means a 175 mm section width, a 65% aspect ratio, radial construction and a 14-inch wheel. That works out to a 113.8 mm sidewall and an overall diameter of about 583.1 mm.
The aspect ratio is a proportion, not a measurement: the same 45 gives a different sidewall height on a different width, and that changes both ride and handling. A lower ratio holds a corner better and transmits more of the road surface.
The size used on kei-class city cars like the Morning and Spark.
What each number means
| 175 | Section width 175 mm |
|---|---|
| 65 | Aspect ratio 113.8 mm (65% × 175 mm) |
| R | Construction Radial |
| 14 | Wheel diameter 355.6 mm |
| Overall diameter | 583.1 mm 23" |
Compatible alternatives
| Size | Overall diameter | Diameter difference |
|---|---|---|
| 165/65R14 | 570.1 mm | -2.2% |
| 185/60R14 | 577.6 mm | -0.9% |
| 175/70R14 | 600.6 mm | +3% |
Load index and speed rating
After the size itself, a tyre wall carries something like 91V. The number is the load index — the weight one tyre can carry, 91 meaning 615 kg — and the letter is the speed rating, V meaning 240 km/h.
Never drop below the load index the manufacturer specified, even if the size matches. The original specification is printed on the label inside the driver’s door.