225/45R17 vs 245/45R17
Going from one to the other changes the overall height by +2.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/45R17 | 245/45R17 | Change |
|---|---|---|---|
| Overall height | 25.0" | 25.7" | +2.8 % |
| Sidewall | 3.99" | 4.34" | +8.9 % |
| Section width | 225 mm | 245 mm | +8.9 % |
| Circumference | 78.5" | 80.7" | +2.8 % |
| Revs per mile | 808 | 785 | -2.8 % |
| Axle height | 12.49" | 12.84" | +9.0 mm |
| Approved rim width | 6–8.5" | 7–9" | overlap 7–8.5" |
Both are approved on a rim 7" to 8.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 225/45R17. Fit 245/45R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.4 mph | +1.4 |
| 70 mph | 72.0 mph | +2.0 |
| 90 mph | 92.6 mph | +2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,284 on the road, so it under-counts by 284. At a true 70 mph the first turns 942 times a minute, the second 916.