165/50R14 vs 145/55R14
Going from one to the other changes the overall height by -1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 165/50R14 | 145/55R14 | Change |
|---|---|---|---|
| Overall height | 20.5" | 20.3" | -1.1 % |
| Sidewall | 3.25" | 3.14" | -3.3 % |
| Section width | 165 mm | 145 mm | -12.1 % |
| Circumference | 64.4" | 63.7" | -1.1 % |
| Revs per mile | 984 | 995 | +1.1 % |
| Axle height | 10.25" | 10.14" | -2.8 mm |
| Approved rim width | 4.5–6" | 4–5.5" | overlap 4.5–5.5" |
Both are approved on a rim 4.5" 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 165/50R14. Fit 145/55R14 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 | 89.0 mph | -1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,894 on the road, so it over-counts by 106. At a true 70 mph the first turns 1148 times a minute, the second 1160.