285/45R20 vs 265/50R20
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/45R20 | 265/50R20 | Change |
|---|---|---|---|
| Overall height | 30.1" | 30.4" | +1.1 % |
| Sidewall | 5.05" | 5.22" | +3.3 % |
| Section width | 285 mm | 265 mm | -7.0 % |
| Circumference | 94.6" | 95.6" | +1.1 % |
| Revs per mile | 670 | 663 | -1.1 % |
| Axle height | 15.05" | 15.22" | +4.3 mm |
| Approved rim width | 8–10.5" | 7.5–9.5" | 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 285/45R20. Fit 265/50R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,111 on the road, so it under-counts by 111. At a true 70 mph the first turns 782 times a minute, the second 773.
What drivers reported
Nobody has filed a complaint naming 285/45R20. 265/50R20 carries 7.