335/45R23 vs 345/40R23
Going from one to the other changes the overall height by -2.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/45R23 | 345/40R23 | Change |
|---|---|---|---|
| Overall height | 34.9" | 33.9" | -2.9 % |
| Sidewall | 5.94" | 5.43" | -8.5 % |
| Section width | 335 mm | 345 mm | +3.0 % |
| Circumference | 109.5" | 106.4" | -2.9 % |
| Revs per mile | 578 | 596 | +2.9 % |
| Axle height | 17.44" | 16.93" | -12.8 mm |
| Approved rim width | 9.5–12.5" | 9.5–12.5" | overlap 9.5–12.5" |
Both are approved on a rim 9.5" 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 335/45R23. Fit 345/40R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.4 mph | -2.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,712 on the road, so it over-counts by 288. At a true 70 mph the first turns 675 times a minute, the second 695.