205/60R13 vs 185/65R13
Going from one to the other changes the overall height by -1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 205/60R13 | 185/65R13 | Change |
|---|---|---|---|
| Overall height | 22.7" | 22.5" | -1.0 % |
| Sidewall | 4.84" | 4.73" | -2.2 % |
| Section width | 205 mm | 185 mm | -9.8 % |
| Circumference | 71.3" | 70.6" | -1.0 % |
| Revs per mile | 889 | 898 | +1.0 % |
| Axle height | 11.34" | 11.23" | -2.8 mm |
| Approved rim width | 5.5–7.5" | 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 205/60R13. Fit 185/65R13 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,905 on the road, so it over-counts by 95. At a true 70 mph the first turns 1037 times a minute, the second 1047.