325/60R19 vs 345/60R19
Going from one to the other changes the overall height by +2.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 325/60R19 | 345/60R19 | Change |
|---|---|---|---|
| Overall height | 34.4" | 35.3" | +2.8 % |
| Sidewall | 7.68" | 8.15" | +6.2 % |
| Section width | 325 mm | 345 mm | +6.2 % |
| Circumference | 107.9" | 110.9" | +2.8 % |
| Revs per mile | 587 | 571 | -2.8 % |
| Axle height | 17.18" | 17.65" | +12.0 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 325/60R19. Fit 345/60R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.4 mph | +1.4 |
| 70 mph | 71.9 mph | +1.9 |
| 90 mph | 92.5 mph | +2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,275 on the road, so it under-counts by 275. At a true 70 mph the first turns 685 times a minute, the second 667.