445/55R22.5 vs 425/60R22.5
Going from one to the other changes the overall height by +1.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 445/55R22.5 | 425/60R22.5 | Change |
|---|---|---|---|
| Overall height | 41.8" | 42.6" | +1.9 % |
| Sidewall | 9.64" | 10.04" | +4.2 % |
| Section width | 445 mm | 425 mm | -4.5 % |
| Circumference | 131.2" | 133.8" | +1.9 % |
| Revs per mile | 483 | 474 | -1.9 % |
| Axle height | 20.89" | 21.29" | +10.3 mm |
| Approved rim width | 13–16" | 12–15" | overlap 13–15" |
Both are approved on a rim 13" to 15" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 445/55R22.5. Fit 425/60R22.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 51.0 mph | +1.0 |
| 70 mph | 71.4 mph | +1.4 |
| 90 mph | 91.7 mph | +1.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,193 on the road, so it under-counts by 193. At a true 70 mph the first turns 563 times a minute, the second 553.