165/55R15 vs 145/65R15
Going from one to the other changes the overall height by +1.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 165/55R15 | 145/65R15 | Change |
|---|---|---|---|
| Overall height | 22.1" | 22.4" | +1.2 % |
| Sidewall | 3.57" | 3.71" | +3.9 % |
| Section width | 165 mm | 145 mm | -12.1 % |
| Circumference | 69.6" | 70.4" | +1.2 % |
| Revs per mile | 911 | 900 | -1.2 % |
| Axle height | 11.07" | 11.21" | +3.5 mm |
| Approved rim width | 4.5–6" | 4–5.5" | overlap 4.5–5.5" |
Both are approved on a rim 4.5" to 5.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 165/55R15. Fit 145/65R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.9 mph | +0.9 |
| 90 mph | 91.1 mph | +1.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,124 on the road, so it under-counts by 124. At a true 70 mph the first turns 1062 times a minute, the second 1049.