225/75R14 vs 205/80R14
Going from one to the other changes the overall height by -1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/75R14 | 205/80R14 | Change |
|---|---|---|---|
| Overall height | 27.3" | 26.9" | -1.4 % |
| Sidewall | 6.64" | 6.46" | -2.8 % |
| Section width | 225 mm | 205 mm | -8.9 % |
| Circumference | 85.7" | 84.6" | -1.4 % |
| Revs per mile | 739 | 749 | +1.4 % |
| Axle height | 13.64" | 13.46" | -4.8 mm |
| Approved rim width | 6–8.5" | 5.5–7.5" | overlap 6–7.5" |
Both are approved on a rim 6" to 7.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 225/75R14. Fit 205/80R14 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.3 mph | -0.7 |
| 70 mph | 69.0 mph | -1.0 |
| 90 mph | 88.8 mph | -1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,863 on the road, so it over-counts by 137. At a true 70 mph the first turns 862 times a minute, the second 874.