145/75R14 vs 155/75R14
Going from one to the other changes the overall height by +2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 145/75R14 | 155/75R14 | Change |
|---|---|---|---|
| Overall height | 22.6" | 23.2" | +2.6 % |
| Sidewall | 4.28" | 4.58" | +6.9 % |
| Section width | 145 mm | 155 mm | +6.9 % |
| Circumference | 70.9" | 72.7" | +2.6 % |
| Revs per mile | 894 | 871 | -2.6 % |
| Axle height | 11.28" | 11.58" | +7.5 mm |
| Approved rim width | 4–5.5" | 4–5.5" | overlap 4–5.5" |
Both are approved on a rim 4" 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 145/75R14. Fit 155/75R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.8 mph | +1.8 |
| 90 mph | 92.4 mph | +2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,262 on the road, so it under-counts by 262. At a true 70 mph the first turns 1043 times a minute, the second 1016.