215/50R20 vs 215/45R20
Going from one to the other changes the overall height by -3.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/50R20 | 215/45R20 | Change |
|---|---|---|---|
| Overall height | 28.5" | 27.6" | -3.0 % |
| Sidewall | 4.23" | 3.81" | -10.0 % |
| Section width | 215 mm | 215 mm | 0.0 % |
| Circumference | 89.4" | 86.8" | -3.0 % |
| Revs per mile | 709 | 730 | +3.0 % |
| Axle height | 14.23" | 13.81" | -10.8 mm |
| Approved rim width | 6–8" | 6–8" | overlap 6–8" |
Both are approved on a rim 6" to 8" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 215/50R20. Fit 215/45R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.5 mph | -1.5 |
| 70 mph | 67.9 mph | -2.1 |
| 90 mph | 87.3 mph | -2.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,703 on the road, so it over-counts by 297. At a true 70 mph the first turns 827 times a minute, the second 852.
What drivers reported
215/50R20 carries 1 complaints. Nobody has filed one naming 215/45R20.