335/55R23 vs 315/55R23
Going from one to the other changes the overall height by -2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/55R23 | 315/55R23 | Change |
|---|---|---|---|
| Overall height | 37.5" | 36.6" | -2.3 % |
| Sidewall | 7.25" | 6.82" | -6.0 % |
| Section width | 335 mm | 315 mm | -6.0 % |
| Circumference | 117.8" | 115.1" | -2.3 % |
| Revs per mile | 538 | 550 | +2.3 % |
| Axle height | 18.75" | 18.32" | -11.0 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 335/55R23. Fit 315/55R23 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 | 68.4 mph | -1.6 |
| 90 mph | 87.9 mph | -2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,769 on the road, so it over-counts by 231. At a true 70 mph the first turns 627 times a minute, the second 642.