335/60R23 vs 315/60R23
Going from one to the other changes the overall height by -2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/60R23 | 315/60R23 | Change |
|---|---|---|---|
| Overall height | 38.8" | 37.9" | -2.4 % |
| Sidewall | 7.91" | 7.44" | -6.0 % |
| Section width | 335 mm | 315 mm | -6.0 % |
| Circumference | 122.0" | 119.0" | -2.4 % |
| Revs per mile | 519 | 532 | +2.4 % |
| Axle height | 19.41" | 18.94" | -12.0 mm |
| Approved rim width | 9.5–12.5" | 8.5–11.5" | 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 335/60R23. Fit 315/60R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.3 mph | -1.7 |
| 90 mph | 87.8 mph | -2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,757 on the road, so it over-counts by 243. At a true 70 mph the first turns 606 times a minute, the second 621.