335/25R23 vs 315/30R23
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 | 335/25R23 | 315/30R23 | Change |
|---|---|---|---|
| Overall height | 29.6" | 30.4" | +2.9 % |
| Sidewall | 3.30" | 3.72" | +12.8 % |
| Section width | 335 mm | 315 mm | -6.0 % |
| Circumference | 93.0" | 95.6" | +2.9 % |
| Revs per mile | 681 | 663 | -2.9 % |
| Axle height | 14.80" | 15.22" | +10.8 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 335/25R23. Fit 315/30R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.4 mph | +1.4 |
| 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 10,286 on the road, so it under-counts by 286. At a true 70 mph the first turns 795 times a minute, the second 773.