355/55R24 vs 345/60R24
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 | 355/55R24 | 345/60R24 | Change |
|---|---|---|---|
| Overall height | 39.4" | 40.3" | +2.3 % |
| Sidewall | 7.69" | 8.15" | +6.0 % |
| Section width | 355 mm | 345 mm | -2.8 % |
| Circumference | 123.7" | 126.6" | +2.3 % |
| Revs per mile | 512 | 500 | -2.3 % |
| Axle height | 19.69" | 20.15" | +11.8 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 355/55R24. Fit 345/60R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,235 on the road, so it under-counts by 235. At a true 70 mph the first turns 598 times a minute, the second 584.