265/70R23 vs 285/65R23
Going from one to the other changes the overall height by -0.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 265/70R23 | 285/65R23 | Change |
|---|---|---|---|
| Overall height | 37.6" | 37.6" | -0.1 % |
| Sidewall | 7.30" | 7.29" | -0.1 % |
| Section width | 265 mm | 285 mm | +7.5 % |
| Circumference | 118.1" | 118.1" | -0.1 % |
| Revs per mile | 536 | 537 | +0.1 % |
| Axle height | 18.80" | 18.79" | -0.3 mm |
| Approved rim width | 7.5–9.5" | 8–10.5" | 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 265/70R23. Fit 285/65R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.0 mph | -0.0 |
| 50 mph | 50.0 mph | -0.0 |
| 70 mph | 70.0 mph | -0.0 |
| 90 mph | 90.0 mph | -0.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,995 on the road, so it over-counts by 5. At a true 70 mph the first turns 626 times a minute, the second 626.