215/45R14 vs 225/40R14
Going from one to the other changes the overall height by -2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/45R14 | 225/40R14 | Change |
|---|---|---|---|
| Overall height | 21.6" | 21.1" | -2.5 % |
| Sidewall | 3.81" | 3.54" | -7.0 % |
| Section width | 215 mm | 225 mm | +4.7 % |
| Circumference | 67.9" | 66.2" | -2.5 % |
| Revs per mile | 933 | 956 | +2.5 % |
| Axle height | 10.81" | 10.54" | -6.8 mm |
| Approved rim width | 6–8" | 6–8.5" | overlap 6–8" |
Both are approved on a rim 6" to 8" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 215/45R14. Fit 225/40R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.3 mph | -1.7 |
| 90 mph | 87.8 mph | -2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,754 on the road, so it over-counts by 246. At a true 70 mph the first turns 1088 times a minute, the second 1116.