355/45R18 vs 335/45R18
Going from one to the other changes the overall height by -2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/45R18 | 335/45R18 | Change |
|---|---|---|---|
| Overall height | 30.6" | 29.9" | -2.3 % |
| Sidewall | 6.29" | 5.94" | -5.6 % |
| Section width | 355 mm | 335 mm | -5.6 % |
| Circumference | 96.1" | 93.8" | -2.3 % |
| Revs per mile | 660 | 675 | +2.3 % |
| Axle height | 15.29" | 14.94" | -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 355/45R18. Fit 335/45R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 87.9 mph | -2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,768 on the road, so it over-counts by 232. At a true 70 mph the first turns 769 times a minute, the second 788.