335/45R18 vs 355/45R18
Going from one to the other changes the overall height by +2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/45R18 | 355/45R18 | Change |
|---|---|---|---|
| Overall height | 29.9" | 30.6" | +2.4 % |
| Sidewall | 5.94" | 6.29" | +6.0 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 93.8" | 96.1" | +2.4 % |
| Revs per mile | 675 | 660 | -2.4 % |
| Axle height | 14.94" | 15.29" | +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 335/45R18. Fit 355/45R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,237 on the road, so it under-counts by 237. At a true 70 mph the first turns 788 times a minute, the second 769.