345/30R19 vs 325/35R19
Going from one to the other changes the overall height by +3.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 345/30R19 | 325/35R19 | Change |
|---|---|---|---|
| Overall height | 27.1" | 28.0" | +3.0 % |
| Sidewall | 4.07" | 4.48" | +9.9 % |
| Section width | 345 mm | 325 mm | -5.8 % |
| Circumference | 85.3" | 87.8" | +3.0 % |
| Revs per mile | 743 | 721 | -3.0 % |
| Axle height | 13.57" | 13.98" | +10.3 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 345/30R19. Fit 325/35R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.9 mph | +0.9 |
| 50 mph | 51.5 mph | +1.5 |
| 70 mph | 72.1 mph | +2.1 |
| 90 mph | 92.7 mph | +2.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,297 on the road, so it under-counts by 297. At a true 70 mph the first turns 867 times a minute, the second 842.