275/55R18 vs 295/50R18
Going from one to the other changes the overall height by -1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 275/55R18 | 295/50R18 | Change |
|---|---|---|---|
| Overall height | 29.9" | 29.6" | -1.0 % |
| Sidewall | 5.95" | 5.81" | -2.5 % |
| Section width | 275 mm | 295 mm | +7.3 % |
| Circumference | 94.0" | 93.0" | -1.0 % |
| Revs per mile | 674 | 681 | +1.0 % |
| Axle height | 14.95" | 14.81" | -3.8 mm |
| Approved rim width | 7.5–10" | 8.5–11" | overlap 8.5–10" |
Both are approved on a rim 8.5" to 10" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 275/55R18. Fit 295/50R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,901 on the road, so it over-counts by 99. At a true 70 mph the first turns 787 times a minute, the second 795.