315/65R18 vs 335/60R18
Going from one to the other changes the overall height by -0.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 315/65R18 | 335/60R18 | Change |
|---|---|---|---|
| Overall height | 34.1" | 33.8" | -0.9 % |
| Sidewall | 8.06" | 7.91" | -1.8 % |
| Section width | 315 mm | 335 mm | +6.3 % |
| Circumference | 107.2" | 106.3" | -0.9 % |
| Revs per mile | 591 | 596 | +0.9 % |
| Axle height | 17.06" | 16.91" | -3.8 mm |
| Approved rim width | 8.5–11.5" | 9.5–12.5" | overlap 9.5–11.5" |
Both are approved on a rim 9.5" to 11.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 315/65R18. Fit 335/60R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.6 mph | -0.4 |
| 70 mph | 69.4 mph | -0.6 |
| 90 mph | 89.2 mph | -0.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,913 on the road, so it over-counts by 87. At a true 70 mph the first turns 690 times a minute, the second 696.