215/45R18 vs 195/50R18
Going from one to the other changes the overall height by +0.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/45R18 | 195/50R18 | Change |
|---|---|---|---|
| Overall height | 25.6" | 25.7" | +0.2 % |
| Sidewall | 3.81" | 3.84" | +0.8 % |
| Section width | 215 mm | 195 mm | -9.3 % |
| Circumference | 80.5" | 80.7" | +0.2 % |
| Revs per mile | 787 | 785 | -0.2 % |
| Axle height | 12.81" | 12.84" | +0.8 mm |
| Approved rim width | 6–8" | 5.5–7" | overlap 6–7" |
Both are approved on a rim 6" to 7" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 215/45R18. Fit 195/50R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.1 mph | +0.1 |
| 50 mph | 50.1 mph | +0.1 |
| 70 mph | 70.2 mph | +0.2 |
| 90 mph | 90.2 mph | +0.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,023 on the road, so it under-counts by 23. At a true 70 mph the first turns 918 times a minute, the second 916.
What drivers reported
215/45R18 carries 5 complaints. Nobody has filed one naming 195/50R18.