245/80R22.5 vs 265/75R22.5
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 | 245/80R22.5 | 265/75R22.5 | Change |
|---|---|---|---|
| Overall height | 37.9" | 38.1" | +0.6 % |
| Sidewall | 7.72" | 7.82" | +1.4 % |
| Section width | 245 mm | 265 mm | +8.2 % |
| Circumference | 119.2" | 119.9" | +0.6 % |
| Revs per mile | 532 | 529 | -0.6 % |
| Axle height | 18.97" | 19.07" | +2.8 mm |
| Approved rim width | 7–9" | 7.5–9.5" | overlap 7.5–9" |
Both are approved on a rim 7.5" to 9" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 245/80R22.5. Fit 265/75R22.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.2 mph | +0.2 |
| 50 mph | 50.3 mph | +0.3 |
| 70 mph | 70.4 mph | +0.4 |
| 90 mph | 90.5 mph | +0.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,057 on the road, so it under-counts by 57. At a true 70 mph the first turns 620 times a minute, the second 617.