285/45R23 vs 265/45R23
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 | 285/45R23 | 265/45R23 | Change |
|---|---|---|---|
| Overall height | 33.1" | 32.4" | -2.1 % |
| Sidewall | 5.05" | 4.69" | -7.0 % |
| Section width | 285 mm | 265 mm | -7.0 % |
| Circumference | 104.0" | 101.8" | -2.1 % |
| Revs per mile | 609 | 623 | +2.1 % |
| Axle height | 16.55" | 16.19" | -9.0 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 285/45R23. Fit 265/45R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.4 mph | -0.6 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.5 mph | -1.5 |
| 90 mph | 88.1 mph | -1.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,786 on the road, so it over-counts by 214. At a true 70 mph the first turns 711 times a minute, the second 726.