155/75R17 vs 175/65R17
Going from one to the other changes the overall height by -0.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 155/75R17 | 175/65R17 | Change |
|---|---|---|---|
| Overall height | 26.2" | 26.0" | -0.8 % |
| Sidewall | 4.58" | 4.48" | -2.2 % |
| Section width | 155 mm | 175 mm | +12.9 % |
| Circumference | 82.2" | 81.5" | -0.8 % |
| Revs per mile | 771 | 777 | +0.8 % |
| Axle height | 13.08" | 12.98" | -2.5 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 155/75R17. Fit 175/65R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.8 mph | -0.2 |
| 50 mph | 49.6 mph | -0.4 |
| 70 mph | 69.5 mph | -0.5 |
| 90 mph | 89.3 mph | -0.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,925 on the road, so it over-counts by 75. At a true 70 mph the first turns 900 times a minute, the second 906.