285/45R21 vs 295/45R21
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/45R21 | 295/45R21 | Change |
|---|---|---|---|
| Overall height | 31.1" | 31.5" | +1.1 % |
| Sidewall | 5.05" | 5.23" | +3.5 % |
| Section width | 285 mm | 295 mm | +3.5 % |
| Circumference | 97.7" | 98.8" | +1.1 % |
| Revs per mile | 649 | 641 | -1.1 % |
| Axle height | 15.55" | 15.73" | +4.5 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 285/45R21. Fit 295/45R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,114 on the road, so it under-counts by 114. At a true 70 mph the first turns 757 times a minute, the second 748.