355/60R19 vs 345/60R19
Going from one to the other changes the overall height by -1.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/60R19 | 345/60R19 | Change |
|---|---|---|---|
| Overall height | 35.8" | 35.3" | -1.3 % |
| Sidewall | 8.39" | 8.15" | -2.8 % |
| Section width | 355 mm | 345 mm | -2.8 % |
| Circumference | 112.4" | 110.9" | -1.3 % |
| Revs per mile | 564 | 571 | +1.3 % |
| Axle height | 17.89" | 17.65" | -6.0 mm |
| Approved rim width | 10–13" | 9.5–12.5" | overlap 10–12.5" |
Both are approved on a rim 10" to 12.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 355/60R19. Fit 345/60R19 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.3 mph | -0.7 |
| 70 mph | 69.1 mph | -0.9 |
| 90 mph | 88.8 mph | -1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,868 on the road, so it over-counts by 132. At a true 70 mph the first turns 658 times a minute, the second 667.