165/55R16 vs 185/45R16
Going from one to the other changes the overall height by -2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 165/55R16 | 185/45R16 | Change |
|---|---|---|---|
| Overall height | 23.1" | 22.6" | -2.6 % |
| Sidewall | 3.57" | 3.28" | -8.3 % |
| Section width | 165 mm | 185 mm | +12.1 % |
| Circumference | 72.7" | 70.9" | -2.6 % |
| Revs per mile | 871 | 894 | +2.6 % |
| Axle height | 11.57" | 11.28" | -7.5 mm |
| Approved rim width | 4.5–6" | 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 165/55R16. Fit 185/45R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.2 mph | -1.8 |
| 90 mph | 87.7 mph | -2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,745 on the road, so it over-counts by 255. At a true 70 mph the first turns 1017 times a minute, the second 1043.