355/60R20 vs 335/60R20
Going from one to the other changes the overall height by -2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/60R20 | 335/60R20 | Change |
|---|---|---|---|
| Overall height | 36.8" | 35.8" | -2.6 % |
| Sidewall | 8.39" | 7.91" | -5.6 % |
| Section width | 355 mm | 335 mm | -5.6 % |
| Circumference | 115.5" | 112.6" | -2.6 % |
| Revs per mile | 548 | 563 | +2.6 % |
| Axle height | 18.39" | 17.91" | -12.0 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 355/60R20. Fit 335/60R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.2 mph | -1.8 |
| 90 mph | 87.7 mph | -2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,743 on the road, so it over-counts by 257. At a true 70 mph the first turns 640 times a minute, the second 657.