205/40R17 vs 195/40R17
Going from one to the other changes the overall height by -1.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 205/40R17 | 195/40R17 | Change |
|---|---|---|---|
| Overall height | 23.5" | 23.1" | -1.3 % |
| Sidewall | 3.23" | 3.07" | -4.9 % |
| Section width | 205 mm | 195 mm | -4.9 % |
| Circumference | 73.7" | 72.7" | -1.3 % |
| Revs per mile | 860 | 872 | +1.3 % |
| Axle height | 11.73" | 11.57" | -4.0 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 205/40R17. Fit 195/40R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.3 mph | -0.7 |
| 70 mph | 69.1 mph | -0.9 |
| 90 mph | 88.8 mph | -1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,866 on the road, so it over-counts by 134. At a true 70 mph the first turns 1003 times a minute, the second 1017.