335/50R20 vs 355/50R20
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 | 335/50R20 | 355/50R20 | Change |
|---|---|---|---|
| Overall height | 33.2" | 34.0" | +2.4 % |
| Sidewall | 6.59" | 6.99" | +6.0 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 104.3" | 106.7" | +2.4 % |
| Revs per mile | 608 | 594 | -2.4 % |
| Axle height | 16.59" | 16.99" | +10.0 mm |
| Approved rim width | 9.5–12.5" | 10–13" | 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 335/50R20. Fit 355/50R20 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 | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,237 on the road, so it under-counts by 237. At a true 70 mph the first turns 709 times a minute, the second 693.