195/40R18 vs 215/40R18
Going from one to the other changes the overall height by +2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 195/40R18 | 215/40R18 | Change |
|---|---|---|---|
| Overall height | 24.1" | 24.8" | +2.6 % |
| Sidewall | 3.07" | 3.39" | +10.3 % |
| Section width | 195 mm | 215 mm | +10.3 % |
| Circumference | 75.8" | 77.8" | +2.6 % |
| Revs per mile | 835 | 814 | -2.6 % |
| Axle height | 12.07" | 12.39" | +8.0 mm |
| Approved rim width | 5.5–7" | 6–8" | 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 195/40R18. Fit 215/40R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.8 mph | +1.8 |
| 90 mph | 92.3 mph | +2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,261 on the road, so it under-counts by 261. At a true 70 mph the first turns 975 times a minute, the second 950.
What drivers reported
Nobody has filed a complaint naming 195/40R18. 215/40R18 carries 2.