175/50R16 vs 165/55R16
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 | 175/50R16 | 165/55R16 | Change |
|---|---|---|---|
| Overall height | 22.9" | 23.1" | +1.1 % |
| Sidewall | 3.44" | 3.57" | +3.7 % |
| Section width | 175 mm | 165 mm | -5.7 % |
| Circumference | 71.9" | 72.7" | +1.1 % |
| Revs per mile | 881 | 871 | -1.1 % |
| Axle height | 11.44" | 11.57" | +3.3 mm |
| Approved rim width | 5–6" | 4.5–6" | 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 175/50R16. Fit 165/55R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,112 on the road, so it under-counts by 112. At a true 70 mph the first turns 1028 times a minute, the second 1017.