225/35R19 vs 205/40R19
Going from one to the other changes the overall height by +1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/35R19 | 205/40R19 | Change |
|---|---|---|---|
| Overall height | 25.2" | 25.5" | +1.0 % |
| Sidewall | 3.10" | 3.23" | +4.1 % |
| Section width | 225 mm | 205 mm | -8.9 % |
| Circumference | 79.2" | 80.0" | +1.0 % |
| Revs per mile | 800 | 792 | -1.0 % |
| Axle height | 12.60" | 12.73" | +3.3 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 225/35R19. Fit 205/40R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.7 mph | +0.7 |
| 90 mph | 90.9 mph | +0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,102 on the road, so it under-counts by 102. At a true 70 mph the first turns 934 times a minute, the second 924.