195/60R15 vs 185/65R15
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 195/60R15 | 185/65R15 | Change |
|---|---|---|---|
| Overall height | 24.2" | 24.5" | +1.1 % |
| Sidewall | 4.61" | 4.73" | +2.8 % |
| Section width | 195 mm | 185 mm | -5.1 % |
| Circumference | 76.1" | 76.9" | +1.1 % |
| Revs per mile | 833 | 824 | -1.1 % |
| Axle height | 12.11" | 12.23" | +3.3 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 195/60R15. Fit 185/65R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.7 mph | +0.7 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,106 on the road, so it under-counts by 106. At a true 70 mph the first turns 972 times a minute, the second 962.