185/55R15 vs 205/45R17
205/45R17 is taller than 185/55R15 by 5.44% — a diameter difference of 1.25″.
What changes between 185/55R15 and 205/45R17
Switching from 185/55R15 to 205/45R17 changes overall diameter by +5.44%, a taller tire by 1.25 inches. This exceeds 5%, which typically requires real fitment work — clearance mods, speedometer recalibration, and careful checking against TPMS and ABS tolerance before driving any distance. Section width moves by +0.79″ (185mm → 205mm), which affects contact patch and fender-well clearance. Sidewall height shifts by -0.38″: a shorter sidewall sharpens steering response at the cost of ride comfort and rim protection. Revs per mile moves by -45, which translates directly to speedometer error — at an indicated 65 mph, actual speed becomes 68.5 mph. The swap also changes rim diameter from 15″ to 17″, meaning new wheels are required. Wheel cost typically dominates the total upsize budget.
| Spec | 185/55R15 | 205/45R17 |
|---|---|---|
| Overall diameter | 23.01″ | 24.26″ |
| Section width | 7.28″ (185 mm) | 8.07″ (205 mm) |
| Sidewall height | 4.01″ (55%) | 3.63″ (45%) |
| Rim diameter | 15″ | 17″ |
| Circumference | 72.29″ | 76.23″ |
| Revs per mile | 876 | 831 |
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
205/45R17
- Diameter
- 24.26″ / 616.3mm
- Section Width
- 8.07″
- Sidewall
- 3.63″ / 92.25mm
- Circumference
- 76.23″
- Revs/Mile
- 831
Speedometer & Diameter Impact
Different rim — new wheels requiredAt an indicated 60 mph, your actual speed is 63.26 mph (101.81 km/h). Your speedometer reads 5.44% low versus actual speed.