255/75R19 vs 275/65R19
Going from one to the other changes the overall height by -2.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/75R19 | 275/65R19 | Change |
|---|---|---|---|
| Overall height | 34.1" | 33.1" | -2.9 % |
| Sidewall | 7.53" | 7.04" | -6.5 % |
| Section width | 255 mm | 275 mm | +7.8 % |
| Circumference | 107.0" | 103.9" | -2.9 % |
| Revs per mile | 592 | 610 | +2.9 % |
| Axle height | 17.03" | 16.54" | -12.5 mm |
| Approved rim width | 7–9.5" | 7.5–10" | 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 255/75R19. Fit 275/65R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.4 mph | -2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,711 on the road, so it over-counts by 289. At a true 70 mph the first turns 691 times a minute, the second 711.