175/70R13 vs 165/70R13
Going from one to the other changes the overall height by -2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/70R13 | 165/70R13 | Change |
|---|---|---|---|
| Overall height | 22.6" | 22.1" | -2.4 % |
| Sidewall | 4.82" | 4.55" | -5.7 % |
| Section width | 175 mm | 165 mm | -5.7 % |
| Circumference | 71.1" | 69.4" | -2.4 % |
| Revs per mile | 891 | 913 | +2.4 % |
| Axle height | 11.32" | 11.05" | -7.0 mm |
| Approved rim width | 5–6" | 4.5–6" | 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 175/70R13. Fit 165/70R13 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.3 mph | -1.7 |
| 90 mph | 87.8 mph | -2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,757 on the road, so it over-counts by 243. At a true 70 mph the first turns 1039 times a minute, the second 1065.