245/70R15 vs 265/65R15
Going from one to the other changes the overall height by +0.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/70R15 | 265/65R15 | Change |
|---|---|---|---|
| Overall height | 28.5" | 28.6" | +0.2 % |
| Sidewall | 6.75" | 6.78" | +0.4 % |
| Section width | 245 mm | 265 mm | +8.2 % |
| Circumference | 89.5" | 89.7" | +0.2 % |
| Revs per mile | 708 | 706 | -0.2 % |
| Axle height | 14.25" | 14.28" | +0.8 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 245/70R15. Fit 265/65R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.1 mph | +0.1 |
| 50 mph | 50.1 mph | +0.1 |
| 70 mph | 70.1 mph | +0.1 |
| 90 mph | 90.2 mph | +0.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,021 on the road, so it under-counts by 21. At a true 70 mph the first turns 825 times a minute, the second 824.