175/50R17 vs 185/50R17
Going from one to the other changes the overall height by +1.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/50R17 | 185/50R17 | Change |
|---|---|---|---|
| Overall height | 23.9" | 24.3" | +1.6 % |
| Sidewall | 3.44" | 3.64" | +5.7 % |
| Section width | 175 mm | 185 mm | +5.7 % |
| Circumference | 75.1" | 76.3" | +1.6 % |
| Revs per mile | 844 | 831 | -1.6 % |
| Axle height | 11.94" | 12.14" | +5.0 mm |
| Approved rim width | 5–6" | 5–6.5" | overlap 5–6" |
Both are approved on a rim 5" to 6" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 175/50R17. Fit 185/50R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.8 mph | +0.8 |
| 70 mph | 71.2 mph | +1.2 |
| 90 mph | 91.5 mph | +1.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,165 on the road, so it under-counts by 165. At a true 70 mph the first turns 985 times a minute, the second 969.