335/65R18 vs 355/65R18
Going from one to the other changes the overall height by +2.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/65R18 | 355/65R18 | Change |
|---|---|---|---|
| Overall height | 35.1" | 36.2" | +2.9 % |
| Sidewall | 8.57" | 9.08" | +6.0 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 110.4" | 113.6" | +2.9 % |
| Revs per mile | 574 | 558 | -2.9 % |
| Axle height | 17.57" | 18.08" | +13.0 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 335/65R18. Fit 355/65R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.5 mph | +1.5 |
| 70 mph | 72.0 mph | +2.0 |
| 90 mph | 92.6 mph | +2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,291 on the road, so it under-counts by 291. At a true 70 mph the first turns 669 times a minute, the second 651.