245/80R23 vs 265/75R23
Going from one to the other changes the overall height by +0.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/80R23 | 265/75R23 | Change |
|---|---|---|---|
| Overall height | 38.4" | 38.6" | +0.6 % |
| Sidewall | 7.72" | 7.82" | +1.4 % |
| Section width | 245 mm | 265 mm | +8.2 % |
| Circumference | 120.7" | 121.4" | +0.6 % |
| Revs per mile | 525 | 522 | -0.6 % |
| Axle height | 19.22" | 19.32" | +2.8 mm |
| Approved rim width | 7–9" | 7.5–9.5" | overlap 7.5–9" |
Both are approved on a rim 7.5" to 9" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 245/80R23. Fit 265/75R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.2 mph | +0.2 |
| 50 mph | 50.3 mph | +0.3 |
| 70 mph | 70.4 mph | +0.4 |
| 90 mph | 90.5 mph | +0.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,056 on the road, so it under-counts by 56. At a true 70 mph the first turns 612 times a minute, the second 609.