165/75R16 vs 185/70R16
Going from one to the other changes the overall height by +1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 165/75R16 | 185/70R16 | Change |
|---|---|---|---|
| Overall height | 25.7" | 26.2" | +1.8 % |
| Sidewall | 4.87" | 5.10" | +4.6 % |
| Section width | 165 mm | 185 mm | +12.1 % |
| Circumference | 80.9" | 82.3" | +1.8 % |
| Revs per mile | 783 | 770 | -1.8 % |
| Axle height | 12.87" | 13.10" | +5.8 mm |
| Approved rim width | 4.5–6" | 5–6.5" | 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 165/75R16. Fit 185/70R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.9 mph | +0.9 |
| 70 mph | 71.2 mph | +1.2 |
| 90 mph | 91.6 mph | +1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,176 on the road, so it under-counts by 176. At a true 70 mph the first turns 914 times a minute, the second 898.