185/65R15 vs 205/65R15
205/65R15 is outside the ±3% rule as a replacement for 185/65R15: the diameter differs by +4.18%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 205/65R15 on a car calibrated for 185/65R15, the speedometer reads 57.6 mph when you're really doing 60, and the odometer under-counts by 4.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.3 mph |
| 45 mph | 46.9 mph |
| 60 mph | 62.5 mph |
| 70 mph | 72.9 mph |
| 80 mph | 83.3 mph |
Other sizes close to 185/65R15
Questions
Can I replace 185/65R15 with 205/65R15?
205/65R15 is outside the ±3% rule as a replacement for 185/65R15: the diameter differs by +4.18%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 185/65R15 and 205/65R15?
205/65R15 is 1.02" taller and 20 mm wider; the sidewall is +0.51". At an indicated 60 mph you'd actually be doing 62.5 mph.
Will 205/65R15 fit on 185/65R15 wheels?
Both use a 15" rim, so the wheel diameter matches; check the wheel's width range for a 205 mm tire and the fender clearance.