325/65R19 vs 345/65R19
Going from one to the other changes the overall height by +2.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 325/65R19 | 345/65R19 | Change |
|---|---|---|---|
| Overall height | 35.6" | 36.7" | +2.9 % |
| Sidewall | 8.32" | 8.83" | +6.2 % |
| Section width | 325 mm | 345 mm | +6.2 % |
| Circumference | 111.9" | 115.2" | +2.9 % |
| Revs per mile | 566 | 550 | -2.9 % |
| Axle height | 17.82" | 18.33" | +13.0 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 325/65R19. Fit 345/65R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.4 mph | +1.4 |
| 70 mph | 72.0 mph | +2.0 |
| 90 mph | 92.6 mph | +2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,287 on the road, so it under-counts by 287. At a true 70 mph the first turns 660 times a minute, the second 642.