265/45R19 vs 285/40R19
Going from one to the other changes the overall height by -1.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 265/45R19 | 285/40R19 | Change |
|---|---|---|---|
| Overall height | 28.4" | 28.0" | -1.5 % |
| Sidewall | 4.69" | 4.49" | -4.4 % |
| Section width | 265 mm | 285 mm | +7.5 % |
| Circumference | 89.2" | 87.9" | -1.5 % |
| Revs per mile | 710 | 721 | +1.5 % |
| Axle height | 14.19" | 13.99" | -5.3 mm |
| Approved rim width | 7.5–9.5" | 8–10.5" | overlap 8–9.5" |
Both are approved on a rim 8" 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 265/45R19. Fit 285/40R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.3 mph | -0.7 |
| 70 mph | 69.0 mph | -1.0 |
| 90 mph | 88.7 mph | -1.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,854 on the road, so it over-counts by 146. At a true 70 mph the first turns 829 times a minute, the second 841.