185/55R15 Tire Size
185/55R15 diameter, sidewall, revolutions per mile, and plus-sizing options.
The 185/55R15 tire size breaks down as: 185 mm section width, 55% aspect ratio, and a 15-inch rim. Below are its real, calculated dimensions.
185/55R15 Calculated Dimensions
| Metric | Value |
|---|---|
| Overall diameter | 23.0 in (585 mm) |
| Sidewall height | 4.0 in (102 mm) |
| Circumference | 72.3 in (1836 mm) |
| Revolutions per mile | 876 |
Typical Fitment
185/55R15 is most often found on sporty economy hatchbacks. Always confirm against the door-jamb placard or owner manual before fitting.
Plus-Sizing Alternatives
These sizes keep the overall diameter close to 185/55R15, so speedometer and gearing stay near stock:
| Size | Diameter | Diameter change |
|---|---|---|
| 195/50R15 | 22.68 in | -1.5% |
| 195/45R16 | 22.91 in | -0.4% |
| 205/35R17 | 22.65 in | -1.6% |
Speedometer Note
If you fit a 195/50R15 instead of 185/55R15, the diameter changes by -1.5%. A taller tire makes your speedometer read low — at a true 60 mph it would show roughly 61 mph. A shorter tire has the opposite effect, so the gauge reads high.
Use the tire calculator to compare 185/55R15 against any other size and see the exact diameter and speedometer difference.
Frequently Asked Questions
What does 185/55R15 mean?
185/55R15 means a 185 mm wide tire with a 55% sidewall aspect ratio mounted on a 15-inch rim. The aspect ratio is the sidewall height as a percentage of the width.
Can I plus-size from 185/55R15?
Yes, as long as the replacement keeps the overall diameter close to stock so the speedometer stays accurate. Common plus-size moves from 185/55R15 are 195/50R15, 195/45R16, 205/35R17.
Will 185/55R15 affect my speedometer?
Only if it differs in diameter from your original size. A taller tire reads low; a shorter tire reads high. Compare the two sizes with the calculator to find the percentage.