225/75R19 vs 205/80R19
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 | 225/75R19 | 205/80R19 | Change |
|---|---|---|---|
| Overall height | 32.3" | 31.9" | -1.2 % |
| Sidewall | 6.64" | 6.46" | -2.8 % |
| Section width | 225 mm | 205 mm | -8.9 % |
| Circumference | 101.4" | 100.3" | -1.2 % |
| Revs per mile | 625 | 632 | +1.2 % |
| Axle height | 16.14" | 15.96" | -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 225/75R19. Fit 205/80R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.4 mph | -0.6 |
| 70 mph | 69.2 mph | -0.8 |
| 90 mph | 89.0 mph | -1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,884 on the road, so it over-counts by 116. At a true 70 mph the first turns 729 times a minute, the second 737.