195/45R15 vs 215/40R15
Going from one to the other changes the overall height by -0.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 195/45R15 | 215/40R15 | Change |
|---|---|---|---|
| Overall height | 21.9" | 21.8" | -0.6 % |
| Sidewall | 3.45" | 3.39" | -2.0 % |
| Section width | 195 mm | 215 mm | +10.3 % |
| Circumference | 68.8" | 68.4" | -0.6 % |
| Revs per mile | 921 | 926 | +0.6 % |
| Axle height | 10.95" | 10.89" | -1.8 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 195/45R15. Fit 215/40R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.8 mph | -0.2 |
| 50 mph | 49.7 mph | -0.3 |
| 70 mph | 69.6 mph | -0.4 |
| 90 mph | 89.4 mph | -0.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,937 on the road, so it over-counts by 63. At a true 70 mph the first turns 1074 times a minute, the second 1081.