215/55R18 vs 195/65R18
Going from one to the other changes the overall height by +2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/55R18 | 195/65R18 | Change |
|---|---|---|---|
| Overall height | 27.3" | 28.0" | +2.5 % |
| Sidewall | 4.66" | 4.99" | +7.2 % |
| Section width | 215 mm | 195 mm | -9.3 % |
| Circumference | 85.8" | 87.9" | +2.5 % |
| Revs per mile | 738 | 721 | -2.5 % |
| Axle height | 13.66" | 13.99" | +8.5 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 215/55R18. Fit 195/65R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.2 mph | +2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,245 on the road, so it under-counts by 245. At a true 70 mph the first turns 862 times a minute, the second 841.
What drivers reported
215/55R18 carries 10 complaints. Nobody has filed one naming 195/65R18.