165/70R15 vs 175/65R15
Going from one to the other changes the overall height by -0.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 165/70R15 | 175/65R15 | Change |
|---|---|---|---|
| Overall height | 24.1" | 24.0" | -0.6 % |
| Sidewall | 4.55" | 4.48" | -1.5 % |
| Section width | 165 mm | 175 mm | +6.1 % |
| Circumference | 75.7" | 75.3" | -0.6 % |
| Revs per mile | 837 | 842 | +0.6 % |
| Axle height | 12.05" | 11.98" | -1.8 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 165/70R15. Fit 175/65R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.8 mph | -0.2 |
| 50 mph | 49.7 mph | -0.3 |
| 70 mph | 69.6 mph | -0.4 |
| 90 mph | 89.5 mph | -0.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,943 on the road, so it over-counts by 57. At a true 70 mph the first turns 977 times a minute, the second 982.