355/50R20 vs 335/50R20
Going from one to the other changes the overall height by -2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/50R20 | 335/50R20 | Change |
|---|---|---|---|
| Overall height | 34.0" | 33.2" | -2.3 % |
| Sidewall | 6.99" | 6.59" | -5.6 % |
| Section width | 355 mm | 335 mm | -5.6 % |
| Circumference | 106.7" | 104.3" | -2.3 % |
| Revs per mile | 594 | 608 | +2.3 % |
| Axle height | 16.99" | 16.59" | -10.0 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 355/50R20. Fit 335/50R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 87.9 mph | -2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,768 on the road, so it over-counts by 232. At a true 70 mph the first turns 693 times a minute, the second 709.