285/50R18 vs 295/45R18
Going from one to the other changes the overall height by -2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/50R18 | 295/45R18 | Change |
|---|---|---|---|
| Overall height | 29.2" | 28.5" | -2.6 % |
| Sidewall | 5.61" | 5.23" | -6.8 % |
| Section width | 285 mm | 295 mm | +3.5 % |
| Circumference | 91.8" | 89.4" | -2.6 % |
| Revs per mile | 690 | 709 | +2.6 % |
| Axle height | 14.61" | 14.23" | -9.8 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 285/50R18. Fit 295/45R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.2 mph | -1.8 |
| 90 mph | 87.6 mph | -2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,737 on the road, so it over-counts by 263. At a true 70 mph the first turns 805 times a minute, the second 827.