225/40R17 vs 205/45R17
Going from one to the other changes the overall height by +0.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/40R17 | 205/45R17 | Change |
|---|---|---|---|
| Overall height | 24.1" | 24.3" | +0.7 % |
| Sidewall | 3.54" | 3.63" | +2.5 % |
| Section width | 225 mm | 205 mm | -8.9 % |
| Circumference | 75.7" | 76.2" | +0.7 % |
| Revs per mile | 837 | 831 | -0.7 % |
| Axle height | 12.04" | 12.13" | +2.3 mm |
| Approved rim width | 6–8.5" | 5.5–7.5" | overlap 6–7.5" |
Both are approved on a rim 6" to 7.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 225/40R17. Fit 205/45R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.2 mph | +0.2 |
| 50 mph | 50.4 mph | +0.4 |
| 70 mph | 70.5 mph | +0.5 |
| 90 mph | 90.7 mph | +0.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,074 on the road, so it under-counts by 74. At a true 70 mph the first turns 977 times a minute, the second 970.
What drivers reported
Nobody has filed a complaint naming 225/40R17. 205/45R17 carries 5.