185/55R15 vs 175/65R15
175/65R15 is taller than 185/55R15 by 4.11% — a diameter difference of 0.95″.
What changes between 185/55R15 and 175/65R15
Switching from 185/55R15 to 175/65R15 changes overall diameter by +4.11%, a taller tire by 0.95 inches. This sits in the 3–5% caution band, where rubbing at full steering lock or suspension compression becomes possible. Leveling kits or fender-liner trims are often needed on lifted trucks. Section width moves by -0.39″ (185mm → 175mm), which affects contact patch and fender-well clearance. Sidewall height shifts by +0.47″: a taller sidewall softens ride quality and adds off-road bump protection, with some loss of steering crispness. Revs per mile moves by -34, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 67.7 mph. Both sizes share the same 15″ rim, so no wheel change is required — this is a pure tire-only swap.
| Spec | 185/55R15 | 175/65R15 |
|---|---|---|
| Overall diameter | 23.01″ | 23.96″ |
| Section width | 7.28″ (185 mm) | 6.89″ (175 mm) |
| Sidewall height | 4.01″ (55%) | 4.48″ (65%) |
| Rim diameter | 15″ | 15″ |
| Circumference | 72.29″ | 75.26″ |
| Revs per mile | 876 | 842 |
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
175/65R15
- Diameter
- 23.96″ / 608.5mm
- Section Width
- 6.89″
- Sidewall
- 4.48″ / 113.75mm
- Circumference
- 75.26″
- Revs/Mile
- 842
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 62.46 mph (100.53 km/h). Your speedometer reads 4.11% low versus actual speed.