185/65R14 vs 175/70R14
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 | 185/65R14 | 175/70R14 | Change |
|---|---|---|---|
| Overall height | 23.5" | 23.6" | +0.8 % |
| Sidewall | 4.73" | 4.82" | +1.9 % |
| Section width | 185 mm | 175 mm | -5.4 % |
| Circumference | 73.7" | 74.3" | +0.8 % |
| Revs per mile | 859 | 853 | -0.8 % |
| Axle height | 11.73" | 11.82" | +2.3 mm |
| Approved rim width | 5–6.5" | 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 185/65R14. Fit 175/70R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.2 mph | +0.2 |
| 50 mph | 50.4 mph | +0.4 |
| 70 mph | 70.5 mph | +0.5 |
| 90 mph | 90.7 mph | +0.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,075 on the road, so it under-counts by 75. At a true 70 mph the first turns 1003 times a minute, the second 995.