185/55R16 vs 245/45R16
245/45R16 is a safe swap for 185/55R16 by the usual ±3% rule: the diameter differs by +2.79%.
Speedometer and odometer
With 245/45R16 on a car calibrated for 185/55R16, the speedometer reads 58.4 mph when you're really doing 60, and the odometer under-counts by 2.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.8 mph |
| 45 mph | 46.3 mph |
| 60 mph | 61.7 mph |
| 70 mph | 72.0 mph |
| 80 mph | 82.2 mph |
Other sizes close to 185/55R16
Questions
Can I replace 185/55R16 with 245/45R16?
245/45R16 is a safe swap for 185/55R16 by the usual ±3% rule: the diameter differs by +2.79%.
What's the difference between 185/55R16 and 245/45R16?
245/45R16 is 0.67" taller and 60 mm wider; the sidewall is +0.33". At an indicated 60 mph you'd actually be doing 61.7 mph.
Will 245/45R16 fit on 185/55R16 wheels?
Both use a 16" rim, so the wheel diameter matches; check the wheel's width range for a 245 mm tire and the fender clearance.