175/55R15 vs 185/55R15
185/55R15 is taller than 175/55R15 by 1.92% — a diameter difference of 0.43″.
What changes between 175/55R15 and 185/55R15
Switching from 175/55R15 to 185/55R15 changes overall diameter by +1.92%, a taller tire by 0.43 inches. This lands inside the ±3% fitment safe zone, so most vehicles will accept the swap without rubbing, speedometer recalibration, or ABS/TPMS complications. Section width moves by +0.39″ (175mm → 185mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.22″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -17, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 66.3 mph. Both sizes share the same 15″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 175/55R15 | 185/55R15 |
|---|---|---|
| Overall diameter | 22.58″ | 23.01″ |
| Section width | 6.89″ (175 mm) | 7.28″ (185 mm) |
| Sidewall height | 3.79″ (55%) | 4.01″ (55%) |
| Rim diameter | 15″ | 15″ |
| Circumference | 70.93″ | 72.29″ |
| Revs per mile | 893 | 876 |
Interactive comparison
275/65R18 or "33" for inch aliases175/55R15
- Diameter
- 22.58″ / 573.5mm
- Section Width
- 6.89″
- Sidewall
- 3.79″ / 96.25mm
- Circumference
- 70.93″
- Revs/Mile
- 893
185/55R15
- Diameter
- 23.01″ / 584.5mm
- Section Width
- 7.28″
- Sidewall
- 4.01″ / 101.75mm
- Circumference
- 72.29″
- Revs/Mile
- 876
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 61.15 mph (98.41 km/h). Your speedometer reads 1.92% low versus actual speed.