335/50R18 vs 355/45R18
Going from one to the other changes the overall height by -2.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/50R18 | 355/45R18 | Change |
|---|---|---|---|
| Overall height | 31.2" | 30.6" | -2.0 % |
| Sidewall | 6.59" | 6.29" | -4.6 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 98.0" | 96.1" | -2.0 % |
| Revs per mile | 647 | 660 | +2.0 % |
| Axle height | 15.59" | 15.29" | -7.8 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 335/50R18. Fit 355/45R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.4 mph | -0.6 |
| 50 mph | 49.0 mph | -1.0 |
| 70 mph | 68.6 mph | -1.4 |
| 90 mph | 88.2 mph | -1.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,804 on the road, so it over-counts by 196. At a true 70 mph the first turns 754 times a minute, the second 769.