285/50R24 vs 305/45R24
Going from one to the other changes the overall height by -1.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/50R24 | 305/45R24 | Change |
|---|---|---|---|
| Overall height | 35.2" | 34.8" | -1.2 % |
| Sidewall | 5.61" | 5.40" | -3.7 % |
| Section width | 285 mm | 305 mm | +7.0 % |
| Circumference | 110.6" | 109.3" | -1.2 % |
| Revs per mile | 573 | 579 | +1.2 % |
| Axle height | 17.61" | 17.40" | -5.3 mm |
| Approved rim width | 8–10.5" | 8.5–11" | overlap 8.5–10.5" |
Both are approved on a rim 8.5" to 10.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 285/50R24. Fit 305/45R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.4 mph | -0.6 |
| 70 mph | 69.2 mph | -0.8 |
| 90 mph | 88.9 mph | -1.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,883 on the road, so it over-counts by 117. At a true 70 mph the first turns 668 times a minute, the second 676.