165/80R15 vs 165/75R15
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 | 165/80R15 | 165/75R15 | Change |
|---|---|---|---|
| Overall height | 25.4" | 24.7" | -2.6 % |
| Sidewall | 5.20" | 4.87" | -6.3 % |
| Section width | 165 mm | 165 mm | 0.0 % |
| Circumference | 79.8" | 77.7" | -2.6 % |
| Revs per mile | 794 | 815 | +2.6 % |
| Axle height | 12.70" | 12.37" | -8.3 mm |
| Approved rim width | 4.5–6" | 4.5–6" | overlap 4.5–6" |
Both are approved on a rim 4.5" to 6" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 165/80R15. Fit 165/75R15 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 9,744 on the road, so it over-counts by 256. At a true 70 mph the first turns 927 times a minute, the second 951.
What drivers reported
165/80R15 carries 4 complaints. Nobody has filed one naming 165/75R15.