215/55R15 vs 225/55R15
Going from one to the other changes the overall height by +1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/55R15 | 225/55R15 | Change |
|---|---|---|---|
| Overall height | 24.3" | 24.7" | +1.8 % |
| Sidewall | 4.66" | 4.87" | +4.7 % |
| Section width | 215 mm | 225 mm | +4.7 % |
| Circumference | 76.4" | 77.7" | +1.8 % |
| Revs per mile | 830 | 815 | -1.8 % |
| Axle height | 12.16" | 12.37" | +5.5 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 215/55R15. Fit 225/55R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.9 mph | +0.9 |
| 70 mph | 71.2 mph | +1.2 |
| 90 mph | 91.6 mph | +1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,178 on the road, so it under-counts by 178. At a true 70 mph the first turns 968 times a minute, the second 951.