245/55R24 vs 245/50R24
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 | 245/55R24 | 245/50R24 | Change |
|---|---|---|---|
| Overall height | 34.6" | 33.6" | -2.8 % |
| Sidewall | 5.31" | 4.82" | -9.1 % |
| Section width | 245 mm | 245 mm | 0.0 % |
| Circumference | 108.7" | 105.7" | -2.8 % |
| Revs per mile | 583 | 599 | +2.8 % |
| Axle height | 17.31" | 16.82" | -12.3 mm |
| Approved rim width | 7–9" | 7–9" | overlap 7–9" |
Both are approved on a rim 7" to 9" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 245/55R24. Fit 245/50R24 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 680 times a minute, the second 699.