185/70R17 vs 205/65R17
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 185/70R17 | 205/65R17 | Change |
|---|---|---|---|
| Overall height | 27.2" | 27.5" | +1.1 % |
| Sidewall | 5.10" | 5.25" | +2.9 % |
| Section width | 185 mm | 205 mm | +10.8 % |
| Circumference | 85.4" | 86.4" | +1.1 % |
| Revs per mile | 742 | 734 | -1.1 % |
| Axle height | 13.60" | 13.75" | +3.8 mm |
| Approved rim width | 5–6.5" | 5.5–7.5" | overlap 5.5–6.5" |
Both are approved on a rim 5.5" to 6.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 185/70R17. Fit 205/65R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,109 on the road, so it under-counts by 109. At a true 70 mph the first turns 865 times a minute, the second 856.