285/55R23 vs 265/55R23
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 | 285/55R23 | 265/55R23 | Change |
|---|---|---|---|
| Overall height | 35.3" | 34.5" | -2.5 % |
| Sidewall | 6.17" | 5.74" | -7.0 % |
| Section width | 285 mm | 265 mm | -7.0 % |
| Circumference | 111.0" | 108.3" | -2.5 % |
| Revs per mile | 571 | 585 | +2.5 % |
| Axle height | 17.67" | 17.24" | -11.0 mm |
| Approved rim width | 8–10.5" | 7.5–9.5" | overlap 8–9.5" |
Both are approved on a rim 8" 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 285/55R23. Fit 265/55R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.3 mph | -1.7 |
| 90 mph | 87.8 mph | -2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,755 on the road, so it over-counts by 245. At a true 70 mph the first turns 666 times a minute, the second 682.