215/85R15 vs 225/85R15
Going from one to the other changes the overall height by +2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/85R15 | 225/85R15 | Change |
|---|---|---|---|
| Overall height | 29.4" | 30.1" | +2.3 % |
| Sidewall | 7.19" | 7.53" | +4.7 % |
| Section width | 215 mm | 225 mm | +4.7 % |
| Circumference | 92.3" | 94.4" | +2.3 % |
| Revs per mile | 686 | 671 | -2.3 % |
| Axle height | 14.69" | 15.03" | +8.5 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 215/85R15. Fit 225/85R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.0 mph | +2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,228 on the road, so it under-counts by 228. At a true 70 mph the first turns 801 times a minute, the second 783.