205/60R13 vs 185/70R13
Going from one to the other changes the overall height by +2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 205/60R13 | 185/70R13 | Change |
|---|---|---|---|
| Overall height | 22.7" | 23.2" | +2.3 % |
| Sidewall | 4.84" | 5.10" | +5.3 % |
| Section width | 205 mm | 185 mm | -9.8 % |
| Circumference | 71.3" | 72.9" | +2.3 % |
| Revs per mile | 889 | 869 | -2.3 % |
| Axle height | 11.34" | 11.60" | +6.5 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 185/70R13 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.0 mph | +2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,226 on the road, so it under-counts by 226. At a true 70 mph the first turns 1037 times a minute, the second 1014.
What drivers reported
Nobody has filed a complaint naming 205/60R13. 185/70R13 carries 6.