255/80R22.5 vs 255/75R22.5
Going from one to the other changes the overall height by -2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/80R22.5 | 255/75R22.5 | Change |
|---|---|---|---|
| Overall height | 38.6" | 37.6" | -2.6 % |
| Sidewall | 8.03" | 7.53" | -6.3 % |
| Section width | 255 mm | 255 mm | 0.0 % |
| Circumference | 121.1" | 118.0" | -2.6 % |
| Revs per mile | 523 | 537 | +2.6 % |
| Axle height | 19.28" | 18.78" | -12.8 mm |
| Approved rim width | 7–9.5" | 7–9.5" | overlap 7–9.5" |
Both are approved on a rim 7" 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 255/80R22.5. Fit 255/75R22.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.2 mph | -1.8 |
| 90 mph | 87.7 mph | -2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,740 on the road, so it over-counts by 260. At a true 70 mph the first turns 610 times a minute, the second 626.
What drivers reported
255/80R22.5 carries 42 complaints. Nobody has filed one naming 255/75R22.5.