205/50R18 vs 195/55R18
Going from one to the other changes the overall height by +1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 205/50R18 | 195/55R18 | Change |
|---|---|---|---|
| Overall height | 26.1" | 26.4" | +1.4 % |
| Sidewall | 4.04" | 4.22" | +4.6 % |
| Section width | 205 mm | 195 mm | -4.9 % |
| Circumference | 81.9" | 83.1" | +1.4 % |
| Revs per mile | 774 | 763 | -1.4 % |
| Axle height | 13.04" | 13.22" | +4.8 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 205/50R18. Fit 195/55R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 71.0 mph | +1.0 |
| 90 mph | 91.3 mph | +1.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,143 on the road, so it under-counts by 143. At a true 70 mph the first turns 903 times a minute, the second 890.
What drivers reported
205/50R18 carries 2 complaints. Nobody has filed one naming 195/55R18.