175/50R17 vs 175/55R17
Going from one to the other changes the overall height by +2.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/50R17 | 175/55R17 | Change |
|---|---|---|---|
| Overall height | 23.9" | 24.6" | +2.9 % |
| Sidewall | 3.44" | 3.79" | +10.0 % |
| Section width | 175 mm | 175 mm | 0.0 % |
| Circumference | 75.1" | 77.2" | +2.9 % |
| Revs per mile | 844 | 821 | -2.9 % |
| Axle height | 11.94" | 12.29" | +8.8 mm |
| Approved rim width | 5–6" | 5–6" | overlap 5–6" |
Both are approved on a rim 5" to 6" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 175/50R17. Fit 175/55R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.4 mph | +1.4 |
| 70 mph | 72.0 mph | +2.0 |
| 90 mph | 92.6 mph | +2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,288 on the road, so it under-counts by 288. At a true 70 mph the first turns 985 times a minute, the second 957.