285/60R22 vs 305/60R22
Going from one to the other changes the overall height by +2.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/60R22 | 305/60R22 | Change |
|---|---|---|---|
| Overall height | 35.5" | 36.4" | +2.7 % |
| Sidewall | 6.73" | 7.20" | +7.0 % |
| Section width | 285 mm | 305 mm | +7.0 % |
| Circumference | 111.4" | 114.4" | +2.7 % |
| Revs per mile | 569 | 554 | -2.7 % |
| Axle height | 17.73" | 18.20" | +12.0 mm |
| Approved rim width | 8–10.5" | 8.5–11" | overlap 8.5–10.5" |
Both are approved on a rim 8.5" to 10.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 285/60R22. Fit 305/60R22 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.9 mph | +1.9 |
| 90 mph | 92.4 mph | +2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,266 on the road, so it under-counts by 266. At a true 70 mph the first turns 663 times a minute, the second 646.