305/35R19 vs 325/30R19
Going from one to the other changes the overall height by -2.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 305/35R19 | 325/30R19 | Change |
|---|---|---|---|
| Overall height | 27.4" | 26.7" | -2.7 % |
| Sidewall | 4.20" | 3.84" | -8.7 % |
| Section width | 305 mm | 325 mm | +6.6 % |
| Circumference | 86.1" | 83.8" | -2.7 % |
| Revs per mile | 736 | 756 | +2.7 % |
| Axle height | 13.70" | 13.34" | -9.3 mm |
| Approved rim width | 8.5–11" | 9–12" | overlap 9–11" |
Both are approved on a rim 9" to 11" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 305/35R19. Fit 325/30R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.1 mph | -1.9 |
| 90 mph | 87.6 mph | -2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,734 on the road, so it over-counts by 266. At a true 70 mph the first turns 859 times a minute, the second 882.
What drivers reported
Nobody has filed a complaint naming 305/35R19. 325/30R19 carries 1.