275/45R23 vs 285/40R23
Going from one to the other changes the overall height by -2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 275/45R23 | 285/40R23 | Change |
|---|---|---|---|
| Overall height | 32.7" | 32.0" | -2.3 % |
| Sidewall | 4.87" | 4.49" | -7.9 % |
| Section width | 275 mm | 285 mm | +3.6 % |
| Circumference | 102.9" | 100.5" | -2.3 % |
| Revs per mile | 616 | 631 | +2.3 % |
| Axle height | 16.37" | 15.99" | -9.8 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 275/45R23. Fit 285/40R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 87.9 mph | -2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,766 on the road, so it over-counts by 234. At a true 70 mph the first turns 719 times a minute, the second 736.
What drivers reported
Nobody has filed a complaint naming 275/45R23. 285/40R23 carries 1.