355/45R24 vs 345/50R24
Going from one to the other changes the overall height by +2.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/45R24 | 345/50R24 | Change |
|---|---|---|---|
| Overall height | 36.6" | 37.6" | +2.7 % |
| Sidewall | 6.29" | 6.79" | +8.0 % |
| Section width | 355 mm | 345 mm | -2.8 % |
| Circumference | 114.9" | 118.1" | +2.7 % |
| Revs per mile | 551 | 537 | -2.7 % |
| Axle height | 18.29" | 18.79" | +12.8 mm |
| Approved rim width | 10–13" | 9.5–12.5" | overlap 10–12.5" |
Both are approved on a rim 10" to 12.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 355/45R24. Fit 345/50R24 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 | 71.9 mph | +1.9 |
| 90 mph | 92.5 mph | +2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,274 on the road, so it under-counts by 274. At a true 70 mph the first turns 643 times a minute, the second 626.