355/45R20 vs 335/50R20
Going from one to the other changes the overall height by +1.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/45R20 | 335/50R20 | Change |
|---|---|---|---|
| Overall height | 32.6" | 33.2" | +1.9 % |
| Sidewall | 6.29" | 6.59" | +4.9 % |
| Section width | 355 mm | 335 mm | -5.6 % |
| Circumference | 102.3" | 104.3" | +1.9 % |
| Revs per mile | 619 | 608 | -1.9 % |
| Axle height | 16.29" | 16.59" | +7.8 mm |
| Approved rim width | 10–13" | 9.5–12.5" | overlap 10–12.5" |
Both are approved on a rim 10" to 12.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 355/45R20. Fit 335/50R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 50.9 mph | +0.9 |
| 70 mph | 71.3 mph | +1.3 |
| 90 mph | 91.7 mph | +1.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,187 on the road, so it under-counts by 187. At a true 70 mph the first turns 722 times a minute, the second 709.