215/40R15 vs 205/45R15
Going from one to the other changes the overall height by +2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/40R15 | 205/45R15 | Change |
|---|---|---|---|
| Overall height | 21.8" | 22.3" | +2.3 % |
| Sidewall | 3.39" | 3.63" | +7.3 % |
| Section width | 215 mm | 205 mm | -4.7 % |
| Circumference | 68.4" | 69.9" | +2.3 % |
| Revs per mile | 926 | 906 | -2.3 % |
| Axle height | 10.89" | 11.13" | +6.3 mm |
| Approved rim width | 6–8" | 5.5–7.5" | overlap 6–7.5" |
Both are approved on a rim 6" to 7.5" 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 205/45R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.0 mph | +2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,226 on the road, so it under-counts by 226. At a true 70 mph the first turns 1081 times a minute, the second 1057.
What drivers reported
Nobody has filed a complaint naming 215/40R15. 205/45R15 carries 2.