185/50R13 vs 175/55R13
Going from one to the other changes the overall height by +1.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 185/50R13 | 175/55R13 | Change |
|---|---|---|---|
| Overall height | 20.3" | 20.6" | +1.5 % |
| Sidewall | 3.64" | 3.79" | +4.1 % |
| Section width | 185 mm | 175 mm | -5.4 % |
| Circumference | 63.7" | 64.7" | +1.5 % |
| Revs per mile | 994 | 980 | -1.5 % |
| Axle height | 10.14" | 10.29" | +3.8 mm |
| Approved rim width | 5–6.5" | 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 185/50R13. Fit 175/55R13 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 71.0 mph | +1.0 |
| 90 mph | 91.3 mph | +1.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,146 on the road, so it under-counts by 146. At a true 70 mph the first turns 1160 times a minute, the second 1143.