335/60R18 vs 355/55R18
Going from one to the other changes the overall height by -1.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/60R18 | 355/55R18 | Change |
|---|---|---|---|
| Overall height | 33.8" | 33.4" | -1.3 % |
| Sidewall | 7.91" | 7.69" | -2.9 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 106.3" | 104.8" | -1.3 % |
| Revs per mile | 596 | 604 | +1.3 % |
| Axle height | 16.91" | 16.69" | -5.8 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 335/60R18. Fit 355/55R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.3 mph | -0.7 |
| 70 mph | 69.1 mph | -0.9 |
| 90 mph | 88.8 mph | -1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,866 on the road, so it over-counts by 134. At a true 70 mph the first turns 696 times a minute, the second 705.