275/55R17 vs 255/55R17
Going from one to the other changes the overall height by -3.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 275/55R17 | 255/55R17 | Change |
|---|---|---|---|
| Overall height | 28.9" | 28.0" | -3.0 % |
| Sidewall | 5.95" | 5.52" | -7.3 % |
| Section width | 275 mm | 255 mm | -7.3 % |
| Circumference | 90.8" | 88.1" | -3.0 % |
| Revs per mile | 698 | 719 | +3.0 % |
| Axle height | 14.45" | 14.02" | -11.0 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 275/55R17. Fit 255/55R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.5 mph | -1.5 |
| 70 mph | 67.9 mph | -2.1 |
| 90 mph | 87.3 mph | -2.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,700 on the road, so it over-counts by 300. At a true 70 mph the first turns 814 times a minute, the second 839.
What drivers reported
275/55R17 carries 2 complaints. Nobody has filed one naming 255/55R17.