185/55R18 vs 195/50R18
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 | 185/55R18 | 195/50R18 | Change |
|---|---|---|---|
| Overall height | 26.0" | 25.7" | -1.3 % |
| Sidewall | 4.01" | 3.84" | -4.2 % |
| Section width | 185 mm | 195 mm | +5.4 % |
| Circumference | 81.7" | 80.7" | -1.3 % |
| Revs per mile | 775 | 785 | +1.3 % |
| Axle height | 13.01" | 12.84" | -4.3 mm |
| Approved rim width | 5–6.5" | 5.5–7" | 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 185/55R18. Fit 195/50R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.4 mph | -0.6 |
| 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 9,871 on the road, so it over-counts by 129. At a true 70 mph the first turns 905 times a minute, the second 916.
What drivers reported
185/55R18 carries 1 complaints. Nobody has filed one naming 195/50R18.