185/80R17 vs 205/70R17
Going from one to the other changes the overall height by -1.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 185/80R17 | 205/70R17 | Change |
|---|---|---|---|
| Overall height | 28.7" | 28.3" | -1.2 % |
| Sidewall | 5.83" | 5.65" | -3.0 % |
| Section width | 185 mm | 205 mm | +10.8 % |
| Circumference | 90.0" | 88.9" | -1.2 % |
| Revs per mile | 704 | 713 | +1.2 % |
| Axle height | 14.33" | 14.15" | -4.5 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 185/80R17. Fit 205/70R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.4 mph | -0.6 |
| 70 mph | 69.1 mph | -0.9 |
| 90 mph | 88.9 mph | -1.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,876 on the road, so it over-counts by 124. At a true 70 mph the first turns 821 times a minute, the second 831.
What drivers reported
Nobody has filed a complaint naming 185/80R17. 205/70R17 carries 1.