245/40R16 vs 265/40R16
Going from one to the other changes the overall height by +2.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/40R16 | 265/40R16 | Change |
|---|---|---|---|
| Overall height | 23.7" | 24.3" | +2.7 % |
| Sidewall | 3.86" | 4.17" | +8.2 % |
| Section width | 245 mm | 265 mm | +8.2 % |
| Circumference | 74.5" | 76.5" | +2.7 % |
| Revs per mile | 850 | 828 | -2.7 % |
| Axle height | 11.86" | 12.17" | +8.0 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 245/40R16. Fit 265/40R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.9 mph | +1.9 |
| 90 mph | 92.4 mph | +2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,266 on the road, so it under-counts by 266. At a true 70 mph the first turns 992 times a minute, the second 966.