275/65R23 vs 265/70R23
Going from one to the other changes the overall height by +1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 275/65R23 | 265/70R23 | Change |
|---|---|---|---|
| Overall height | 37.1" | 37.6" | +1.4 % |
| Sidewall | 7.04" | 7.30" | +3.8 % |
| Section width | 275 mm | 265 mm | -3.6 % |
| Circumference | 116.5" | 118.1" | +1.4 % |
| Revs per mile | 544 | 536 | -1.4 % |
| Axle height | 18.54" | 18.80" | +6.8 mm |
| Approved rim width | 7.5–10" | 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 275/65R23. Fit 265/70R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 71.0 mph | +1.0 |
| 90 mph | 91.3 mph | +1.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,143 on the road, so it under-counts by 143. At a true 70 mph the first turns 635 times a minute, the second 626.