255/60R15 vs 265/60R15
Going from one to the other changes the overall height by +1.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/60R15 | 265/60R15 | Change |
|---|---|---|---|
| Overall height | 27.0" | 27.5" | +1.7 % |
| Sidewall | 6.02" | 6.26" | +3.9 % |
| Section width | 255 mm | 265 mm | +3.9 % |
| Circumference | 85.0" | 86.5" | +1.7 % |
| Revs per mile | 746 | 733 | -1.7 % |
| Axle height | 13.52" | 13.76" | +6.0 mm |
| Approved rim width | 7–9.5" | 7.5–9.5" | overlap 7.5–9.5" |
Both are approved on a rim 7.5" to 9.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 255/60R15. Fit 265/60R15 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 10,175 on the road, so it under-counts by 175. At a true 70 mph the first turns 870 times a minute, the second 855.