225/45R22 vs 225/40R22
Going from one to the other changes the overall height by -3.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/45R22 | 225/40R22 | Change |
|---|---|---|---|
| Overall height | 30.0" | 29.1" | -3.0 % |
| Sidewall | 3.99" | 3.54" | -11.1 % |
| Section width | 225 mm | 225 mm | 0.0 % |
| Circumference | 94.2" | 91.4" | -3.0 % |
| Revs per mile | 673 | 693 | +3.0 % |
| Axle height | 14.99" | 14.54" | -11.3 mm |
| Approved rim width | 6–8.5" | 6–8.5" | overlap 6–8.5" |
Both are approved on a rim 6" 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 225/45R22. Fit 225/40R22 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.5 mph | -1.5 |
| 70 mph | 67.9 mph | -2.1 |
| 90 mph | 87.3 mph | -2.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,704 on the road, so it over-counts by 296. At a true 70 mph the first turns 785 times a minute, the second 809.