275/40R24 vs 265/45R24
Going from one to the other changes the overall height by +2.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 275/40R24 | 265/45R24 | Change |
|---|---|---|---|
| Overall height | 32.7" | 33.4" | +2.2 % |
| Sidewall | 4.33" | 4.69" | +8.4 % |
| Section width | 275 mm | 265 mm | -3.6 % |
| Circumference | 102.6" | 104.9" | +2.2 % |
| Revs per mile | 617 | 604 | -2.2 % |
| Axle height | 16.33" | 16.69" | +9.3 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 275/40R24. Fit 265/45R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.0 mph | +2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,223 on the road, so it under-counts by 223. At a true 70 mph the first turns 720 times a minute, the second 705.