205/45R16 vs 185/55R16
185/55R16 is outside the ±3% rule as a replacement for 205/45R16: the diameter differs by +3.22%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 185/55R16 on a car calibrated for 205/45R16, the speedometer reads 58.1 mph when you're really doing 60, and the odometer under-counts by 3.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.0 mph |
| 45 mph | 46.4 mph |
| 60 mph | 61.9 mph |
| 70 mph | 72.3 mph |
| 80 mph | 82.6 mph |
Other sizes close to 205/45R16
Questions
Can I replace 205/45R16 with 185/55R16?
185/55R16 is outside the ±3% rule as a replacement for 205/45R16: the diameter differs by +3.22%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 205/45R16 and 185/55R16?
185/55R16 is 0.75" taller and 20 mm narrower; the sidewall is +0.37". At an indicated 60 mph you'd actually be doing 61.9 mph.
Will 185/55R16 fit on 205/45R16 wheels?
Both use a 16" rim, so the wheel diameter matches; check the wheel's width range for a 185 mm tire and the fender clearance.