175/75R13 vs 165/80R13
Going from one to the other changes the overall height by +0.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 175/75R13 | 165/80R13 | Change |
|---|---|---|---|
| Overall height | 23.3" | 23.4" | +0.3 % |
| Sidewall | 5.17" | 5.20" | +0.6 % |
| Section width | 175 mm | 165 mm | -5.7 % |
| Circumference | 73.3" | 73.5" | +0.3 % |
| Revs per mile | 864 | 862 | -0.3 % |
| Axle height | 11.67" | 11.70" | +0.8 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 175/75R13. Fit 165/80R13 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.1 mph | +0.1 |
| 50 mph | 50.1 mph | +0.1 |
| 70 mph | 70.2 mph | +0.2 |
| 90 mph | 90.2 mph | +0.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,025 on the road, so it under-counts by 25. At a true 70 mph the first turns 1008 times a minute, the second 1006.