195/70R17 vs 175/80R17
Going from one to the other changes the overall height by +1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 195/70R17 | 175/80R17 | Change |
|---|---|---|---|
| Overall height | 27.7" | 28.0" | +1.0 % |
| Sidewall | 5.37" | 5.51" | +2.6 % |
| Section width | 195 mm | 175 mm | -10.3 % |
| Circumference | 87.2" | 88.0" | +1.0 % |
| Revs per mile | 727 | 720 | -1.0 % |
| Axle height | 13.87" | 14.01" | +3.5 mm |
| Approved rim width | 5.5–7" | 5–6" | overlap 5.5–6" |
Both are approved on a rim 5.5" to 6" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 195/70R17. Fit 175/80R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.7 mph | +0.7 |
| 90 mph | 90.9 mph | +0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,099 on the road, so it under-counts by 99. At a true 70 mph the first turns 848 times a minute, the second 840.