285/60R21 vs 295/60R21
Going from one to the other changes the overall height by +1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/60R21 | 295/60R21 | Change |
|---|---|---|---|
| Overall height | 34.5" | 34.9" | +1.4 % |
| Sidewall | 6.73" | 6.97" | +3.5 % |
| Section width | 285 mm | 295 mm | +3.5 % |
| Circumference | 108.3" | 109.8" | +1.4 % |
| Revs per mile | 585 | 577 | -1.4 % |
| Axle height | 17.23" | 17.47" | +6.0 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 285/60R21. Fit 295/60R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 71.0 mph | +1.0 |
| 90 mph | 91.2 mph | +1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,137 on the road, so it under-counts by 137. At a true 70 mph the first turns 683 times a minute, the second 673.