255/55R24 vs 275/55R24
Going from one to the other changes the overall height by +2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/55R24 | 275/55R24 | Change |
|---|---|---|---|
| Overall height | 35.0" | 35.9" | +2.5 % |
| Sidewall | 5.52" | 5.95" | +7.8 % |
| Section width | 255 mm | 275 mm | +7.8 % |
| Circumference | 110.1" | 112.8" | +2.5 % |
| Revs per mile | 576 | 562 | -2.5 % |
| Axle height | 17.52" | 17.95" | +11.0 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 255/55R24. Fit 275/55R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.2 mph | +2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,247 on the road, so it under-counts by 247. At a true 70 mph the first turns 671 times a minute, the second 655.