265/30R22 vs 285/30R22
Going from one to the other changes the overall height by +1.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 265/30R22 | 285/30R22 | Change |
|---|---|---|---|
| Overall height | 28.3" | 28.7" | +1.7 % |
| Sidewall | 3.13" | 3.37" | +7.5 % |
| Section width | 265 mm | 285 mm | +7.5 % |
| Circumference | 88.8" | 90.3" | +1.7 % |
| Revs per mile | 714 | 702 | -1.7 % |
| Axle height | 14.13" | 14.37" | +6.0 mm |
| Approved rim width | 7.5–9.5" | 8–10.5" | overlap 8–9.5" |
Both are approved on a rim 8" 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 265/30R22. Fit 285/30R22 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.8 mph | +0.8 |
| 70 mph | 71.2 mph | +1.2 |
| 90 mph | 91.5 mph | +1.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,167 on the road, so it under-counts by 167. At a true 70 mph the first turns 833 times a minute, the second 819.