205/70R15 vs 225/60R15
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 | 205/70R15 | 225/60R15 | Change |
|---|---|---|---|
| Overall height | 26.3" | 25.6" | -2.5 % |
| Sidewall | 5.65" | 5.31" | -5.9 % |
| Section width | 205 mm | 225 mm | +9.8 % |
| Circumference | 82.6" | 80.5" | -2.5 % |
| Revs per mile | 767 | 787 | +2.5 % |
| Axle height | 13.15" | 12.81" | -8.5 mm |
| Approved rim width | 5.5–7.5" | 6–8.5" | overlap 6–7.5" |
Both are approved on a rim 6" to 7.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 205/70R15. Fit 225/60R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.2 mph | -1.8 |
| 90 mph | 87.7 mph | -2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,746 on the road, so it over-counts by 254. At a true 70 mph the first turns 895 times a minute, the second 918.