265/65R21 vs 285/60R21
Going from one to the other changes the overall height by -0.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 265/65R21 | 285/60R21 | Change |
|---|---|---|---|
| Overall height | 34.6" | 34.5" | -0.3 % |
| Sidewall | 6.78" | 6.73" | -0.7 % |
| Section width | 265 mm | 285 mm | +7.5 % |
| Circumference | 108.6" | 108.3" | -0.3 % |
| Revs per mile | 584 | 585 | +0.3 % |
| Axle height | 17.28" | 17.23" | -1.3 mm |
| Approved rim width | 7.5–9.5" | 8–10.5" | overlap 8–9.5" |
Both are approved on a rim 8" to 9.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 265/65R21. Fit 285/60R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.9 mph | -0.1 |
| 50 mph | 49.9 mph | -0.1 |
| 70 mph | 69.8 mph | -0.2 |
| 90 mph | 89.7 mph | -0.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,972 on the road, so it over-counts by 28. At a true 70 mph the first turns 681 times a minute, the second 683.