125/70R14 vs 125/75R14
Going from one to the other changes the overall height by +2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 125/70R14 | 125/75R14 | Change |
|---|---|---|---|
| Overall height | 20.9" | 21.4" | +2.4 % |
| Sidewall | 3.44" | 3.69" | +7.1 % |
| Section width | 125 mm | 125 mm | 0.0 % |
| Circumference | 65.6" | 67.2" | +2.4 % |
| Revs per mile | 965 | 943 | -2.4 % |
| Axle height | 10.44" | 10.69" | +6.3 mm |
| Approved rim width | 3.5–4.5" | 3.5–4.5" | overlap 3.5–4.5" |
Both are approved on a rim 3.5" to 4.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 125/70R14. Fit 125/75R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,236 on the road, so it under-counts by 236. At a true 70 mph the first turns 1126 times a minute, the second 1100.
What drivers reported
125/70R14 carries 1 complaints. Nobody has filed one naming 125/75R14.