275/60R23 vs 285/60R23
Going from one to the other changes the overall height by +1.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 275/60R23 | 285/60R23 | Change |
|---|---|---|---|
| Overall height | 36.0" | 36.5" | +1.3 % |
| Sidewall | 6.50" | 6.73" | +3.6 % |
| Section width | 275 mm | 285 mm | +3.6 % |
| Circumference | 113.1" | 114.6" | +1.3 % |
| Revs per mile | 560 | 553 | -1.3 % |
| Axle height | 18.00" | 18.23" | +6.0 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 275/60R23. Fit 285/60R23 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 | 70.9 mph | +0.9 |
| 90 mph | 91.2 mph | +1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,131 on the road, so it under-counts by 131. At a true 70 mph the first turns 654 times a minute, the second 645.