215/35R17 vs 205/40R17
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 | 215/35R17 | 205/40R17 | Change |
|---|---|---|---|
| Overall height | 22.9" | 23.5" | +2.3 % |
| Sidewall | 2.96" | 3.23" | +9.0 % |
| Section width | 215 mm | 205 mm | -4.7 % |
| Circumference | 72.0" | 73.7" | +2.3 % |
| Revs per mile | 880 | 860 | -2.3 % |
| Axle height | 11.46" | 11.73" | +6.8 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 215/35R17. Fit 205/40R17 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 | 71.6 mph | +1.6 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,232 on the road, so it under-counts by 232. At a true 70 mph the first turns 1026 times a minute, the second 1003.