185/75R17 vs 205/70R17
Going from one to the other changes the overall height by +1.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 185/75R17 | 205/70R17 | Change |
|---|---|---|---|
| Overall height | 27.9" | 28.3" | +1.3 % |
| Sidewall | 5.46" | 5.65" | +3.4 % |
| Section width | 185 mm | 205 mm | +10.8 % |
| Circumference | 87.7" | 88.9" | +1.3 % |
| Revs per mile | 722 | 713 | -1.3 % |
| Axle height | 13.96" | 14.15" | +4.8 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 185/75R17. Fit 205/70R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 70.9 mph | +0.9 |
| 90 mph | 91.2 mph | +1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,134 on the road, so it under-counts by 134. At a true 70 mph the first turns 843 times a minute, the second 831.
What drivers reported
Nobody has filed a complaint naming 185/75R17. 205/70R17 carries 1.