335/45R20 vs 355/45R20
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 | 335/45R20 | 355/45R20 | Change |
|---|---|---|---|
| Overall height | 31.9" | 32.6" | +2.2 % |
| Sidewall | 5.94" | 6.29" | +6.0 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 100.1" | 102.3" | +2.2 % |
| Revs per mile | 633 | 619 | -2.2 % |
| Axle height | 15.94" | 16.29" | +9.0 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 335/45R20. Fit 355/45R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.0 mph | +2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,222 on the road, so it under-counts by 222. At a true 70 mph the first turns 738 times a minute, the second 722.