165/80R15 vs 175/80R15
Going from one to the other changes the overall height by +2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 165/80R15 | 175/80R15 | Change |
|---|---|---|---|
| Overall height | 25.4" | 26.0" | +2.5 % |
| Sidewall | 5.20" | 5.51" | +6.1 % |
| Section width | 165 mm | 175 mm | +6.1 % |
| Circumference | 79.8" | 81.8" | +2.5 % |
| Revs per mile | 794 | 775 | -2.5 % |
| Axle height | 12.70" | 13.01" | +8.0 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 165/80R15. Fit 175/80R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.2 mph | +2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,248 on the road, so it under-counts by 248. At a true 70 mph the first turns 927 times a minute, the second 904.
What drivers reported
165/80R15 carries 4 complaints. Nobody has filed one naming 175/80R15.