265/75R24.5 vs 275/70R24.5
Going from one to the other changes the overall height by -1.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 265/75R24.5 | 275/70R24.5 | Change |
|---|---|---|---|
| Overall height | 40.1" | 39.7" | -1.2 % |
| Sidewall | 7.82" | 7.58" | -3.1 % |
| Section width | 265 mm | 275 mm | +3.8 % |
| Circumference | 126.1" | 124.6" | -1.2 % |
| Revs per mile | 502 | 509 | +1.2 % |
| Axle height | 20.07" | 19.83" | -6.3 mm |
| Approved rim width | 7.5–9.5" | 7.5–10" | 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 265/75R24.5. Fit 275/70R24.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.4 mph | -0.6 |
| 70 mph | 69.1 mph | -0.9 |
| 90 mph | 88.9 mph | -1.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,877 on the road, so it over-counts by 123. At a true 70 mph the first turns 586 times a minute, the second 593.