355/65R18 vs 335/65R18
Going from one to the other changes the overall height by -2.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/65R18 | 335/65R18 | Change |
|---|---|---|---|
| Overall height | 36.2" | 35.1" | -2.8 % |
| Sidewall | 9.08" | 8.57" | -5.6 % |
| Section width | 355 mm | 335 mm | -5.6 % |
| Circumference | 113.6" | 110.4" | -2.8 % |
| Revs per mile | 558 | 574 | +2.8 % |
| Axle height | 18.08" | 17.57" | -13.0 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 355/65R18. Fit 335/65R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.5 mph | -2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,717 on the road, so it over-counts by 283. At a true 70 mph the first turns 651 times a minute, the second 669.