215/75R15 vs 225/75R15
Going from one to the other changes the overall height by +2.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/75R15 | 225/75R15 | Change |
|---|---|---|---|
| Overall height | 27.7" | 28.3" | +2.1 % |
| Sidewall | 6.35" | 6.64" | +4.7 % |
| Section width | 215 mm | 225 mm | +4.7 % |
| Circumference | 87.0" | 88.9" | +2.1 % |
| Revs per mile | 728 | 713 | -2.1 % |
| Axle height | 13.85" | 14.14" | +7.5 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 215/75R15. Fit 225/75R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.5 mph | +1.5 |
| 90 mph | 91.9 mph | +1.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,213 on the road, so it under-counts by 213. At a true 70 mph the first turns 850 times a minute, the second 832.