265/50R18 vs 245/50R18
Going from one to the other changes the overall height by -2.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 265/50R18 | 245/50R18 | Change |
|---|---|---|---|
| Overall height | 28.4" | 27.6" | -2.8 % |
| Sidewall | 5.22" | 4.82" | -7.5 % |
| Section width | 265 mm | 245 mm | -7.5 % |
| Circumference | 89.3" | 86.9" | -2.8 % |
| Revs per mile | 709 | 730 | +2.8 % |
| Axle height | 14.22" | 13.82" | -10.0 mm |
| Approved rim width | 7.5–9.5" | 7–9" | 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 265/50R18. Fit 245/50R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.1 mph | -1.9 |
| 90 mph | 87.5 mph | -2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,723 on the road, so it over-counts by 277. At a true 70 mph the first turns 828 times a minute, the second 851.