185/55R15 vs 175/55R15
175/55R15 is shorter than 185/55R15 by 1.88% — a diameter difference of 0.43″.
What changes between 185/55R15 and 175/55R15
Switching from 185/55R15 to 175/55R15 changes overall diameter by -1.88%, a shorter 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″ (185mm → 175mm), which affects contact patch and fender-well clearance. Sidewall height shifts by -0.22″: a shorter sidewall sharpens steering response at the cost of ride comfort and rim protection. Revs per mile moves by +17, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 63.8 mph. Both sizes share the same 15″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 185/55R15 | 175/55R15 |
|---|---|---|
| Overall diameter | 23.01″ | 22.58″ |
| Section width | 7.28″ (185 mm) | 6.89″ (175 mm) |
| Sidewall height | 4.01″ (55%) | 3.79″ (55%) |
| Rim diameter | 15″ | 15″ |
| Circumference | 72.29″ | 70.93″ |
| Revs per mile | 876 | 893 |
Interactive comparison
275/65R18 or "33" for inch aliases185/55R15
- Diameter
- 23.01″ / 584.5mm
- Section Width
- 7.28″
- Sidewall
- 4.01″ / 101.75mm
- Circumference
- 72.29″
- Revs/Mile
- 876
175/55R15
- Diameter
- 22.58″ / 573.5mm
- Section Width
- 6.89″
- Sidewall
- 3.79″ / 96.25mm
- Circumference
- 70.93″
- Revs/Mile
- 893
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 58.87 mph (94.74 km/h). Your speedometer reads 1.88% high versus actual speed.