305/40R19 vs 295/45R19
Going from one to the other changes the overall height by +3.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 305/40R19 | 295/45R19 | Change |
|---|---|---|---|
| Overall height | 28.6" | 29.5" | +3.0 % |
| Sidewall | 4.80" | 5.23" | +8.8 % |
| Section width | 305 mm | 295 mm | -3.3 % |
| Circumference | 89.9" | 92.5" | +3.0 % |
| Revs per mile | 705 | 685 | -3.0 % |
| Axle height | 14.30" | 14.73" | +10.8 mm |
| Approved rim width | 8.5–11" | 8.5–11" | overlap 8.5–11" |
Both are approved on a rim 8.5" to 11" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 305/40R19. Fit 295/45R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.5 mph | +1.5 |
| 70 mph | 72.1 mph | +2.1 |
| 90 mph | 92.7 mph | +2.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,296 on the road, so it under-counts by 296. At a true 70 mph the first turns 823 times a minute, the second 799.