305/25R19 vs 325/25R19
Going from one to the other changes the overall height by +1.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 305/25R19 | 325/25R19 | Change |
|---|---|---|---|
| Overall height | 25.0" | 25.4" | +1.6 % |
| Sidewall | 3.00" | 3.20" | +6.6 % |
| Section width | 305 mm | 325 mm | +6.6 % |
| Circumference | 78.6" | 79.8" | +1.6 % |
| Revs per mile | 807 | 794 | -1.6 % |
| Axle height | 12.50" | 12.70" | +5.0 mm |
| Approved rim width | 8.5–11" | 9–12" | overlap 9–11" |
Both are approved on a rim 9" to 11" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 305/25R19. Fit 325/25R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.8 mph | +0.8 |
| 70 mph | 71.1 mph | +1.1 |
| 90 mph | 91.4 mph | +1.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,157 on the road, so it under-counts by 157. At a true 70 mph the first turns 941 times a minute, the second 926.