335/40R24 vs 325/45R24
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 | 335/40R24 | 325/45R24 | Change |
|---|---|---|---|
| Overall height | 34.6" | 35.5" | +2.8 % |
| Sidewall | 5.28" | 5.76" | +9.1 % |
| Section width | 335 mm | 325 mm | -3.0 % |
| Circumference | 108.5" | 111.6" | +2.8 % |
| Revs per mile | 584 | 568 | -2.8 % |
| Axle height | 17.28" | 17.76" | +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 335/40R24. Fit 325/45R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.4 mph | +1.4 |
| 70 mph | 72.0 mph | +2.0 |
| 90 mph | 92.5 mph | +2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,279 on the road, so it under-counts by 279. At a true 70 mph the first turns 681 times a minute, the second 663.