305/60R19 vs 325/55R19
Going from one to the other changes the overall height by -1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 305/60R19 | 325/55R19 | Change |
|---|---|---|---|
| Overall height | 33.4" | 33.1" | -1.0 % |
| Sidewall | 7.20" | 7.04" | -2.3 % |
| Section width | 305 mm | 325 mm | +6.6 % |
| Circumference | 105.0" | 103.9" | -1.0 % |
| Revs per mile | 604 | 610 | +1.0 % |
| Axle height | 16.70" | 16.54" | -4.3 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 305/60R19. Fit 325/55R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,900 on the road, so it over-counts by 100. At a true 70 mph the first turns 704 times a minute, the second 711.