195/60R13 vs 185/60R13
Going from one to the other changes the overall height by -2.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 195/60R13 | 185/60R13 | Change |
|---|---|---|---|
| Overall height | 22.2" | 21.7" | -2.1 % |
| Sidewall | 4.61" | 4.37" | -5.1 % |
| Section width | 195 mm | 185 mm | -5.1 % |
| Circumference | 69.8" | 68.3" | -2.1 % |
| Revs per mile | 908 | 928 | +2.1 % |
| Axle height | 11.11" | 10.87" | -6.0 mm |
| Approved rim width | 5.5–7" | 5–6.5" | overlap 5.5–6.5" |
Both are approved on a rim 5.5" to 6.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 195/60R13. Fit 185/60R13 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.4 mph | -0.6 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.5 mph | -1.5 |
| 90 mph | 88.1 mph | -1.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,787 on the road, so it over-counts by 213. At a true 70 mph the first turns 1059 times a minute, the second 1082.