345/60R23 vs 355/55R23
Going from one to the other changes the overall height by -2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 345/60R23 | 355/55R23 | Change |
|---|---|---|---|
| Overall height | 39.3" | 38.4" | -2.4 % |
| Sidewall | 8.15" | 7.69" | -5.7 % |
| Section width | 345 mm | 355 mm | +2.9 % |
| Circumference | 123.5" | 120.6" | -2.4 % |
| Revs per mile | 513 | 526 | +2.4 % |
| Axle height | 19.65" | 19.19" | -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 345/60R23. Fit 355/55R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 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 9,765 on the road, so it over-counts by 235. At a true 70 mph the first turns 599 times a minute, the second 613.