155/80R15 vs 175/75R15
Going from one to the other changes the overall height by +2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 155/80R15 | 175/75R15 | Change |
|---|---|---|---|
| Overall height | 24.8" | 25.3" | +2.3 % |
| Sidewall | 4.88" | 5.17" | +5.8 % |
| Section width | 155 mm | 175 mm | +12.9 % |
| Circumference | 77.8" | 79.6" | +2.3 % |
| Revs per mile | 814 | 796 | -2.3 % |
| Axle height | 12.38" | 12.67" | +7.3 mm |
| Approved rim width | 4–5.5" | 5–6" | overlap 5–5.5" |
Both are approved on a rim 5" to 5.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 155/80R15. Fit 175/75R15 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 | 71.6 mph | +1.6 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,231 on the road, so it under-counts by 231. At a true 70 mph the first turns 950 times a minute, the second 929.
What drivers reported
155/80R15 carries 1 complaints. Nobody has filed one naming 175/75R15.