265/55R23 vs 255/60R23
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 | 265/55R23 | 255/60R23 | Change |
|---|---|---|---|
| Overall height | 34.5" | 35.0" | +1.7 % |
| Sidewall | 5.74" | 6.02" | +5.0 % |
| Section width | 265 mm | 255 mm | -3.8 % |
| Circumference | 108.3" | 110.1" | +1.7 % |
| Revs per mile | 585 | 575 | -1.7 % |
| Axle height | 17.24" | 17.52" | +7.3 mm |
| Approved rim width | 7.5–9.5" | 7–9.5" | 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 265/55R23. Fit 255/60R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.8 mph | +0.8 |
| 70 mph | 71.2 mph | +1.2 |
| 90 mph | 91.5 mph | +1.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,166 on the road, so it under-counts by 166. At a true 70 mph the first turns 682 times a minute, the second 671.