215/40R15 vs 195/40R15
Going from one to the other changes the overall height by -2.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/40R15 | 195/40R15 | Change |
|---|---|---|---|
| Overall height | 21.8" | 21.1" | -2.9 % |
| Sidewall | 3.39" | 3.07" | -9.3 % |
| Section width | 215 mm | 195 mm | -9.3 % |
| Circumference | 68.4" | 66.4" | -2.9 % |
| Revs per mile | 926 | 954 | +2.9 % |
| Axle height | 10.89" | 10.57" | -8.0 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 215/40R15. Fit 195/40R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.4 mph | -2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,711 on the road, so it over-counts by 289. At a true 70 mph the first turns 1081 times a minute, the second 1113.