165/60R15 vs 175/55R15
Going from one to the other changes the overall height by -0.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 165/60R15 | 175/55R15 | Change |
|---|---|---|---|
| Overall height | 22.8" | 22.6" | -0.9 % |
| Sidewall | 3.90" | 3.79" | -2.8 % |
| Section width | 165 mm | 175 mm | +6.1 % |
| Circumference | 71.6" | 70.9" | -0.9 % |
| Revs per mile | 885 | 893 | +0.9 % |
| Axle height | 11.40" | 11.29" | -2.8 mm |
| Approved rim width | 4.5–6" | 5–6" | 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 165/60R15. Fit 175/55R15 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 9,905 on the road, so it over-counts by 95. At a true 70 mph the first turns 1032 times a minute, the second 1042.