325/40R19 vs 345/40R19
Going from one to the other changes the overall height by +2.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 325/40R19 | 345/40R19 | Change |
|---|---|---|---|
| Overall height | 29.2" | 29.9" | +2.2 % |
| Sidewall | 5.12" | 5.43" | +6.2 % |
| Section width | 325 mm | 345 mm | +6.2 % |
| Circumference | 91.8" | 93.8" | +2.2 % |
| Revs per mile | 690 | 675 | -2.2 % |
| Axle height | 14.62" | 14.93" | +8.0 mm |
| Approved rim width | 9–12" | 9.5–12.5" | overlap 9.5–12" |
Both are approved on a rim 9.5" to 12" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 325/40R19. Fit 345/40R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.5 mph | +1.5 |
| 90 mph | 91.9 mph | +1.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,215 on the road, so it under-counts by 215. At a true 70 mph the first turns 805 times a minute, the second 788.