335/65R20 vs 355/60R20
Going from one to the other changes the overall height by -1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/65R20 | 355/60R20 | Change |
|---|---|---|---|
| Overall height | 37.1" | 36.8" | -1.0 % |
| Sidewall | 8.57" | 8.39" | -2.2 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 116.7" | 115.5" | -1.0 % |
| Revs per mile | 543 | 548 | +1.0 % |
| Axle height | 18.57" | 18.39" | -4.8 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 335/65R20. Fit 355/60R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,899 on the road, so it over-counts by 101. At a true 70 mph the first turns 633 times a minute, the second 640.