355/60R18 vs 335/65R18
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/60R18 | 335/65R18 | Change |
|---|---|---|---|
| Overall height | 34.8" | 35.1" | +1.1 % |
| Sidewall | 8.39" | 8.57" | +2.2 % |
| Section width | 355 mm | 335 mm | -5.6 % |
| Circumference | 109.2" | 110.4" | +1.1 % |
| Revs per mile | 580 | 574 | -1.1 % |
| Axle height | 17.39" | 17.57" | +4.8 mm |
| Approved rim width | 10–13" | 9.5–12.5" | 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 355/60R18. Fit 335/65R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,108 on the road, so it under-counts by 108. At a true 70 mph the first turns 677 times a minute, the second 669.