275/65R24 vs 285/60R24
Going from one to the other changes the overall height by -1.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 275/65R24 | 285/60R24 | Change |
|---|---|---|---|
| Overall height | 38.1" | 37.5" | -1.6 % |
| Sidewall | 7.04" | 6.73" | -4.3 % |
| Section width | 275 mm | 285 mm | +3.6 % |
| Circumference | 119.6" | 117.7" | -1.6 % |
| Revs per mile | 530 | 538 | +1.6 % |
| Axle height | 19.04" | 18.73" | -7.8 mm |
| Approved rim width | 7.5–10" | 8–10.5" | overlap 8–10" |
Both are approved on a rim 8" to 10" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 275/65R24. Fit 285/60R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.2 mph | -0.8 |
| 70 mph | 68.9 mph | -1.1 |
| 90 mph | 88.6 mph | -1.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,840 on the road, so it over-counts by 160. At a true 70 mph the first turns 618 times a minute, the second 628.