175/50R14 vs 155/55R14
Going from one to the other changes the overall height by -0.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/50R14 | 155/55R14 | Change |
|---|---|---|---|
| Overall height | 20.9" | 20.7" | -0.8 % |
| Sidewall | 3.44" | 3.36" | -2.6 % |
| Section width | 175 mm | 155 mm | -11.4 % |
| Circumference | 65.6" | 65.1" | -0.8 % |
| Revs per mile | 965 | 974 | +0.8 % |
| Axle height | 10.44" | 10.36" | -2.3 mm |
| Approved rim width | 5–6" | 4–5.5" | overlap 5–5.5" |
Both are approved on a rim 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 175/50R14. Fit 155/55R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.6 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 9,915 on the road, so it over-counts by 85. At a true 70 mph the first turns 1126 times a minute, the second 1136.