285/65R21 vs 295/60R21
Going from one to the other changes the overall height by -1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/65R21 | 295/60R21 | Change |
|---|---|---|---|
| Overall height | 35.6" | 34.9" | -1.8 % |
| Sidewall | 7.29" | 6.97" | -4.5 % |
| Section width | 285 mm | 295 mm | +3.5 % |
| Circumference | 111.8" | 109.8" | -1.8 % |
| Revs per mile | 567 | 577 | +1.8 % |
| Axle height | 17.79" | 17.47" | -8.3 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 285/65R21. Fit 295/60R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.1 mph | -0.9 |
| 70 mph | 68.7 mph | -1.3 |
| 90 mph | 88.4 mph | -1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,817 on the road, so it over-counts by 183. At a true 70 mph the first turns 661 times a minute, the second 673.