145/55R14 vs 155/50R14
Going from one to the other changes the overall height by -0.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 145/55R14 | 155/50R14 | Change |
|---|---|---|---|
| Overall height | 20.3" | 20.1" | -0.9 % |
| Sidewall | 3.14" | 3.05" | -2.8 % |
| Section width | 145 mm | 155 mm | +6.9 % |
| Circumference | 63.7" | 63.2" | -0.9 % |
| Revs per mile | 995 | 1003 | +0.9 % |
| Axle height | 10.14" | 10.05" | -2.2 mm |
| Approved rim width | 4–5.5" | 4–5.5" | overlap 4–5.5" |
Both are approved on a rim 4" to 5.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 145/55R14. Fit 155/50R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.6 mph | -0.4 |
| 70 mph | 69.4 mph | -0.6 |
| 90 mph | 89.2 mph | -0.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,913 on the road, so it over-counts by 87. At a true 70 mph the first turns 1160 times a minute, the second 1170.