165/60R13 vs 185/50R13
Going from one to the other changes the overall height by -2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 165/60R13 | 185/50R13 | Change |
|---|---|---|---|
| Overall height | 20.8" | 20.3" | -2.5 % |
| Sidewall | 3.90" | 3.64" | -6.6 % |
| Section width | 165 mm | 185 mm | +12.1 % |
| Circumference | 65.3" | 63.7" | -2.5 % |
| Revs per mile | 970 | 994 | +2.5 % |
| Axle height | 10.40" | 10.14" | -6.5 mm |
| Approved rim width | 4.5–6" | 5–6.5" | 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 165/60R13. Fit 185/50R13 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.3 mph | -1.7 |
| 90 mph | 87.8 mph | -2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,754 on the road, so it over-counts by 246. At a true 70 mph the first turns 1131 times a minute, the second 1160.