255/50R18 vs 265/45R18
Going from one to the other changes the overall height by -2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/50R18 | 265/45R18 | Change |
|---|---|---|---|
| Overall height | 28.0" | 27.4" | -2.3 % |
| Sidewall | 5.02" | 4.69" | -6.5 % |
| Section width | 255 mm | 265 mm | +3.9 % |
| Circumference | 88.1" | 86.0" | -2.3 % |
| Revs per mile | 719 | 736 | +2.3 % |
| Axle height | 14.02" | 13.69" | -8.3 mm |
| Approved rim width | 7–9.5" | 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 255/50R18. Fit 265/45R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 87.9 mph | -2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,768 on the road, so it over-counts by 232. At a true 70 mph the first turns 839 times a minute, the second 859.
What drivers reported
255/50R18 carries 1 complaints. Nobody has filed one naming 265/45R18.