165/70R15 vs 175/70R15
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 | 165/70R15 | 175/70R15 | Change |
|---|---|---|---|
| Overall height | 24.1" | 24.6" | +2.3 % |
| Sidewall | 4.55" | 4.82" | +6.1 % |
| Section width | 165 mm | 175 mm | +6.1 % |
| Circumference | 75.7" | 77.4" | +2.3 % |
| Revs per mile | 837 | 818 | -2.3 % |
| Axle height | 12.05" | 12.32" | +7.0 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 165/70R15. Fit 175/70R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.1 mph | +1.1 |
| 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 10,229 on the road, so it under-counts by 229. At a true 70 mph the first turns 977 times a minute, the second 955.