205/60R18 vs 195/65R18
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 | 205/60R18 | 195/65R18 | Change |
|---|---|---|---|
| Overall height | 27.7" | 28.0" | +1.1 % |
| Sidewall | 4.84" | 4.99" | +3.0 % |
| Section width | 205 mm | 195 mm | -4.9 % |
| Circumference | 87.0" | 87.9" | +1.1 % |
| Revs per mile | 728 | 721 | -1.1 % |
| Axle height | 13.84" | 13.99" | +3.8 mm |
| Approved rim width | 5.5–7.5" | 5.5–7" | overlap 5.5–7" |
Both are approved on a rim 5.5" to 7" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 205/60R18. Fit 195/65R18 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 10,107 on the road, so it under-counts by 107. At a true 70 mph the first turns 850 times a minute, the second 841.