175/55R16 vs 185/55R16
Going from one to the other changes the overall height by +1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/55R16 | 185/55R16 | Change |
|---|---|---|---|
| Overall height | 23.6" | 24.0" | +1.8 % |
| Sidewall | 3.79" | 4.01" | +5.7 % |
| Section width | 175 mm | 185 mm | +5.7 % |
| Circumference | 74.1" | 75.4" | +1.8 % |
| Revs per mile | 855 | 840 | -1.8 % |
| Axle height | 11.79" | 12.01" | +5.5 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 175/55R16. Fit 185/55R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 50.9 mph | +0.9 |
| 70 mph | 71.3 mph | +1.3 |
| 90 mph | 91.7 mph | +1.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,184 on the road, so it under-counts by 184. At a true 70 mph the first turns 998 times a minute, the second 980.