335/50R18 vs 355/50R18
Going from one to the other changes the overall height by +2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/50R18 | 355/50R18 | Change |
|---|---|---|---|
| Overall height | 31.2" | 32.0" | +2.5 % |
| Sidewall | 6.59" | 6.99" | +6.0 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 98.0" | 100.5" | +2.5 % |
| Revs per mile | 647 | 631 | -2.5 % |
| Axle height | 15.59" | 15.99" | +10.0 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 335/50R18. Fit 355/50R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.8 mph | +1.8 |
| 90 mph | 92.3 mph | +2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,252 on the road, so it under-counts by 252. At a true 70 mph the first turns 754 times a minute, the second 736.