285/40R22 vs 305/40R22
Going from one to the other changes the overall height by +2.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/40R22 | 305/40R22 | Change |
|---|---|---|---|
| Overall height | 31.0" | 31.6" | +2.0 % |
| Sidewall | 4.49" | 4.80" | +7.0 % |
| Section width | 285 mm | 305 mm | +7.0 % |
| Circumference | 97.3" | 99.3" | +2.0 % |
| Revs per mile | 651 | 638 | -2.0 % |
| Axle height | 15.49" | 15.80" | +8.0 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 285/40R22. Fit 305/40R22 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 | 91.8 mph | +1.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,203 on the road, so it under-counts by 203. At a true 70 mph the first turns 760 times a minute, the second 744.
What drivers reported
Nobody has filed a complaint naming 285/40R22. 305/40R22 carries 7.