185/65R15 vs 165/75R15
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 185/65R15 | 165/75R15 | Change |
|---|---|---|---|
| Overall height | 24.5" | 24.7" | +1.1 % |
| Sidewall | 4.73" | 4.87" | +2.9 % |
| Section width | 185 mm | 165 mm | -10.8 % |
| Circumference | 76.9" | 77.7" | +1.1 % |
| Revs per mile | 824 | 815 | -1.1 % |
| Axle height | 12.23" | 12.37" | +3.5 mm |
| Approved rim width | 5–6.5" | 4.5–6" | 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 185/65R15. Fit 165/75R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,113 on the road, so it under-counts by 113. At a true 70 mph the first turns 962 times a minute, the second 951.
What drivers reported
185/65R15 carries 80 complaints. Nobody has filed one naming 165/75R15.