335/40R23 vs 325/45R23
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 | 335/40R23 | 325/45R23 | Change |
|---|---|---|---|
| Overall height | 33.6" | 34.5" | +2.9 % |
| Sidewall | 5.28" | 5.76" | +9.1 % |
| Section width | 335 mm | 325 mm | -3.0 % |
| Circumference | 105.4" | 108.4" | +2.9 % |
| Revs per mile | 601 | 584 | -2.9 % |
| Axle height | 16.78" | 17.26" | +12.3 mm |
| Approved rim width | 9.5–12.5" | 9–12" | 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 335/40R23. Fit 325/45R23 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 10,287 on the road, so it under-counts by 287. At a true 70 mph the first turns 701 times a minute, the second 682.