245/65R18 vs 265/60R18
Going from one to the other changes the overall height by -0.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/65R18 | 265/60R18 | Change |
|---|---|---|---|
| Overall height | 30.5" | 30.5" | -0.1 % |
| Sidewall | 6.27" | 6.26" | -0.2 % |
| Section width | 245 mm | 265 mm | +8.2 % |
| Circumference | 95.9" | 95.9" | -0.1 % |
| Revs per mile | 660 | 661 | +0.1 % |
| Axle height | 15.27" | 15.26" | -0.3 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 245/65R18. Fit 265/60R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.0 mph | -0.0 |
| 50 mph | 50.0 mph | -0.0 |
| 70 mph | 70.0 mph | -0.0 |
| 90 mph | 89.9 mph | -0.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,994 on the road, so it over-counts by 6. At a true 70 mph the first turns 770 times a minute, the second 771.