175/60R17 vs 185/55R17
Going from one to the other changes the overall height by -1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/60R17 | 185/55R17 | Change |
|---|---|---|---|
| Overall height | 25.3" | 25.0" | -1.0 % |
| Sidewall | 4.13" | 4.01" | -3.1 % |
| Section width | 175 mm | 185 mm | +5.7 % |
| Circumference | 79.4" | 78.6" | -1.0 % |
| Revs per mile | 798 | 806 | +1.0 % |
| Axle height | 12.63" | 12.51" | -3.3 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 175/60R17. Fit 185/55R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,899 on the road, so it over-counts by 101. At a true 70 mph the first turns 931 times a minute, the second 941.