295/45R20 vs 285/50R20
Going from one to the other changes the overall height by +2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 295/45R20 | 285/50R20 | Change |
|---|---|---|---|
| Overall height | 30.5" | 31.2" | +2.5 % |
| Sidewall | 5.23" | 5.61" | +7.3 % |
| Section width | 295 mm | 285 mm | -3.4 % |
| Circumference | 95.7" | 98.1" | +2.5 % |
| Revs per mile | 662 | 646 | -2.5 % |
| Axle height | 15.23" | 15.61" | +9.8 mm |
| Approved rim width | 8.5–11" | 8–10.5" | overlap 8.5–10.5" |
Both are approved on a rim 8.5" to 10.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 295/45R20. Fit 285/50R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.8 mph | +1.8 |
| 90 mph | 92.3 mph | +2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,252 on the road, so it under-counts by 252. At a true 70 mph the first turns 773 times a minute, the second 754.
What drivers reported
Nobody has filed a complaint naming 295/45R20. 285/50R20 carries 9.