185/55R15 vs 165/65R15
Going from one to the other changes the overall height by +1.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 185/55R15 | 165/65R15 | Change |
|---|---|---|---|
| Overall height | 23.0" | 23.4" | +1.9 % |
| Sidewall | 4.01" | 4.22" | +5.4 % |
| Section width | 185 mm | 165 mm | -10.8 % |
| Circumference | 72.3" | 73.7" | +1.9 % |
| Revs per mile | 876 | 860 | -1.9 % |
| Axle height | 11.51" | 11.72" | +5.5 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 185/55R15. Fit 165/65R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 50.9 mph | +0.9 |
| 70 mph | 71.3 mph | +1.3 |
| 90 mph | 91.7 mph | +1.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,188 on the road, so it under-counts by 188. At a true 70 mph the first turns 1022 times a minute, the second 1004.
What drivers reported
185/55R15 carries 3 complaints. Nobody has filed one naming 165/65R15.