275/35R19 vs 255/40R19
Going from one to the other changes the overall height by +1.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 275/35R19 | 255/40R19 | Change |
|---|---|---|---|
| Overall height | 26.6" | 27.0" | +1.7 % |
| Sidewall | 3.79" | 4.02" | +6.0 % |
| Section width | 275 mm | 255 mm | -7.3 % |
| Circumference | 83.5" | 84.9" | +1.7 % |
| Revs per mile | 759 | 746 | -1.7 % |
| Axle height | 13.29" | 13.52" | +5.8 mm |
| Approved rim width | 7.5–10" | 7–9.5" | 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 275/35R19. Fit 255/40R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.9 mph | +0.9 |
| 70 mph | 71.2 mph | +1.2 |
| 90 mph | 91.5 mph | +1.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,170 on the road, so it under-counts by 170. At a true 70 mph the first turns 885 times a minute, the second 870.
What drivers reported
275/35R19 carries 4 complaints. Nobody has filed one naming 255/40R19.