345/55R24 vs 355/55R24
Going from one to the other changes the overall height by +1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 345/55R24 | 355/55R24 | Change |
|---|---|---|---|
| Overall height | 38.9" | 39.4" | +1.1 % |
| Sidewall | 7.47" | 7.69" | +2.9 % |
| Section width | 345 mm | 355 mm | +2.9 % |
| Circumference | 122.3" | 123.7" | +1.1 % |
| Revs per mile | 518 | 512 | -1.1 % |
| Axle height | 19.47" | 19.69" | +5.5 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 345/55R24. Fit 355/55R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,111 on the road, so it under-counts by 111. At a true 70 mph the first turns 604 times a minute, the second 598.