345/50R19 vs 325/55R19
Going from one to the other changes the overall height by +1.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 345/50R19 | 325/55R19 | Change |
|---|---|---|---|
| Overall height | 32.6" | 33.1" | +1.5 % |
| Sidewall | 6.79" | 7.04" | +3.6 % |
| Section width | 345 mm | 325 mm | -5.8 % |
| Circumference | 102.4" | 103.9" | +1.5 % |
| Revs per mile | 619 | 610 | -1.5 % |
| Axle height | 16.29" | 16.54" | +6.3 mm |
| Approved rim width | 9.5–12.5" | 9–12" | 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 345/50R19. Fit 325/55R19 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 10,151 on the road, so it under-counts by 151. At a true 70 mph the first turns 722 times a minute, the second 711.