205/50R18 vs 195/50R18
Going from one to the other changes the overall height by -1.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 205/50R18 | 195/50R18 | Change |
|---|---|---|---|
| Overall height | 26.1" | 25.7" | -1.5 % |
| Sidewall | 4.04" | 3.84" | -4.9 % |
| Section width | 205 mm | 195 mm | -4.9 % |
| Circumference | 81.9" | 80.7" | -1.5 % |
| Revs per mile | 774 | 785 | +1.5 % |
| Axle height | 13.04" | 12.84" | -5.0 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 205/50R18. Fit 195/50R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.2 mph | -0.8 |
| 70 mph | 68.9 mph | -1.1 |
| 90 mph | 88.6 mph | -1.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,849 on the road, so it over-counts by 151. At a true 70 mph the first turns 903 times a minute, the second 916.
What drivers reported
205/50R18 carries 2 complaints. Nobody has filed one naming 195/50R18.