355/45R20 vs 335/45R20
Going from one to the other changes the overall height by -2.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/45R20 | 335/45R20 | Change |
|---|---|---|---|
| Overall height | 32.6" | 31.9" | -2.2 % |
| Sidewall | 6.29" | 5.94" | -5.6 % |
| Section width | 355 mm | 335 mm | -5.6 % |
| Circumference | 102.3" | 100.1" | -2.2 % |
| Revs per mile | 619 | 633 | +2.2 % |
| Axle height | 16.29" | 15.94" | -9.0 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 355/45R20. Fit 335/45R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.5 mph | -1.5 |
| 90 mph | 88.0 mph | -2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,782 on the road, so it over-counts by 218. At a true 70 mph the first turns 722 times a minute, the second 738.