225/75R19 vs 215/75R19
Going from one to the other changes the overall height by -1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/75R19 | 215/75R19 | Change |
|---|---|---|---|
| Overall height | 32.3" | 31.7" | -1.8 % |
| Sidewall | 6.64" | 6.35" | -4.4 % |
| Section width | 225 mm | 215 mm | -4.4 % |
| Circumference | 101.4" | 99.6" | -1.8 % |
| Revs per mile | 625 | 636 | +1.8 % |
| Axle height | 16.14" | 15.85" | -7.5 mm |
| Approved rim width | 6–8.5" | 6–8" | overlap 6–8" |
Both are approved on a rim 6" to 8" 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 215/75R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.1 mph | -0.9 |
| 70 mph | 68.7 mph | -1.3 |
| 90 mph | 88.4 mph | -1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,817 on the road, so it over-counts by 183. At a true 70 mph the first turns 729 times a minute, the second 742.