345/60R24 vs 355/55R24
Going from one to the other changes the overall height by -2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 345/60R24 | 355/55R24 | Change |
|---|---|---|---|
| Overall height | 40.3" | 39.4" | -2.3 % |
| Sidewall | 8.15" | 7.69" | -5.7 % |
| Section width | 345 mm | 355 mm | +2.9 % |
| Circumference | 126.6" | 123.7" | -2.3 % |
| Revs per mile | 500 | 512 | +2.3 % |
| Axle height | 20.15" | 19.69" | -11.8 mm |
| Approved rim width | 9.5–12.5" | 10–13" | 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 345/60R24. Fit 355/55R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 87.9 mph | -2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,770 on the road, so it over-counts by 230. At a true 70 mph the first turns 584 times a minute, the second 598.