285/40R23 vs 275/45R23
Going from one to the other changes the overall height by +2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/40R23 | 275/45R23 | Change |
|---|---|---|---|
| Overall height | 32.0" | 32.7" | +2.4 % |
| Sidewall | 4.49" | 4.87" | +8.6 % |
| Section width | 285 mm | 275 mm | -3.5 % |
| Circumference | 100.5" | 102.9" | +2.4 % |
| Revs per mile | 631 | 616 | -2.4 % |
| Axle height | 15.99" | 16.37" | +9.8 mm |
| Approved rim width | 8–10.5" | 7.5–10" | 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 285/40R23. Fit 275/45R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.2 mph | +2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,240 on the road, so it under-counts by 240. At a true 70 mph the first turns 736 times a minute, the second 719.
What drivers reported
285/40R23 carries 1 complaints. Nobody has filed one naming 275/45R23.