335/30R23 vs 315/35R23
Going from one to the other changes the overall height by +2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/30R23 | 315/35R23 | Change |
|---|---|---|---|
| Overall height | 30.9" | 31.7" | +2.5 % |
| Sidewall | 3.96" | 4.34" | +9.7 % |
| Section width | 335 mm | 315 mm | -6.0 % |
| Circumference | 97.1" | 99.5" | +2.5 % |
| Revs per mile | 652 | 637 | -2.5 % |
| Axle height | 15.46" | 15.84" | +9.8 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 335/30R23. Fit 315/35R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.2 mph | +2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,248 on the road, so it under-counts by 248. At a true 70 mph the first turns 761 times a minute, the second 743.