325/35R22 vs 345/30R22
Going from one to the other changes the overall height by -2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 325/35R22 | 345/30R22 | Change |
|---|---|---|---|
| Overall height | 31.0" | 30.1" | -2.6 % |
| Sidewall | 4.48" | 4.07" | -9.0 % |
| Section width | 325 mm | 345 mm | +6.2 % |
| Circumference | 97.3" | 94.7" | -2.6 % |
| Revs per mile | 651 | 669 | +2.6 % |
| Axle height | 15.48" | 15.07" | -10.3 mm |
| Approved rim width | 9–12" | 9.5–12.5" | overlap 9.5–12" |
Both are approved on a rim 9.5" to 12" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 325/35R22. Fit 345/30R22 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.2 mph | -1.8 |
| 90 mph | 87.7 mph | -2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,739 on the road, so it over-counts by 261. At a true 70 mph the first turns 760 times a minute, the second 780.