325/45R23 vs 335/40R23
Going from one to the other changes the overall height by -2.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 325/45R23 | 335/40R23 | Change |
|---|---|---|---|
| Overall height | 34.5" | 33.6" | -2.8 % |
| Sidewall | 5.76" | 5.28" | -8.4 % |
| Section width | 325 mm | 335 mm | +3.1 % |
| Circumference | 108.4" | 105.4" | -2.8 % |
| Revs per mile | 584 | 601 | +2.8 % |
| Axle height | 17.26" | 16.78" | -12.3 mm |
| Approved rim width | 9–12" | 9.5–12.5" | overlap 9.5–12" |
Both are approved on a rim 9.5" to 12" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 325/45R23. Fit 335/40R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.5 mph | -2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,721 on the road, so it over-counts by 279. At a true 70 mph the first turns 682 times a minute, the second 701.