205/45R16 vs 205/40R17
205/40R17 is a safe swap for 205/45R16 by the usual ±3% rule: the diameter differs by +0.83%.
Speedometer and odometer
With 205/40R17 on a car calibrated for 205/45R16, the speedometer reads 59.5 mph when you're really doing 60, and the odometer under-counts by 0.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.4 mph |
| 60 mph | 60.5 mph |
| 70 mph | 70.6 mph |
| 80 mph | 80.7 mph |
Other sizes close to 205/45R16
Questions
Can I replace 205/45R16 with 205/40R17?
205/40R17 is a safe swap for 205/45R16 by the usual ±3% rule: the diameter differs by +0.83%.
What's the difference between 205/45R16 and 205/40R17?
205/40R17 is 0.19" taller and 0 mm wider; the sidewall is -0.40". At an indicated 60 mph you'd actually be doing 60.5 mph.
Will 205/40R17 fit on 205/45R16 wheels?
No — 205/45R16 needs a 16" wheel and 205/40R17 a 17" wheel. This is a plus/minus-size swap that changes wheels too.