255/55R23 vs 275/50R23
Going from one to the other changes the overall height by -0.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/55R23 | 275/50R23 | Change |
|---|---|---|---|
| Overall height | 34.0" | 33.8" | -0.6 % |
| Sidewall | 5.52" | 5.41" | -2.0 % |
| Section width | 255 mm | 275 mm | +7.8 % |
| Circumference | 107.0" | 106.3" | -0.6 % |
| Revs per mile | 592 | 596 | +0.6 % |
| Axle height | 17.02" | 16.91" | -2.8 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 255/55R23. Fit 275/50R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.8 mph | -0.2 |
| 50 mph | 49.7 mph | -0.3 |
| 70 mph | 69.6 mph | -0.4 |
| 90 mph | 89.4 mph | -0.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,936 on the road, so it over-counts by 64. At a true 70 mph the first turns 691 times a minute, the second 696.