325/50R24 vs 345/45R24
Going from one to the other changes the overall height by -1.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 325/50R24 | 345/45R24 | Change |
|---|---|---|---|
| Overall height | 36.8" | 36.2" | -1.6 % |
| Sidewall | 6.40" | 6.11" | -4.5 % |
| Section width | 325 mm | 345 mm | +6.2 % |
| Circumference | 115.6" | 113.8" | -1.6 % |
| Revs per mile | 548 | 557 | +1.6 % |
| Axle height | 18.40" | 18.11" | -7.3 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 325/50R24. Fit 345/45R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.2 mph | -0.8 |
| 70 mph | 68.9 mph | -1.1 |
| 90 mph | 88.6 mph | -1.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,845 on the road, so it over-counts by 155. At a true 70 mph the first turns 639 times a minute, the second 650.