235/75R22 vs 225/75R22
Going from one to the other changes the overall height by -1.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/75R22 | 225/75R22 | Change |
|---|---|---|---|
| Overall height | 35.9" | 35.3" | -1.6 % |
| Sidewall | 6.94" | 6.64" | -4.3 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 112.7" | 110.9" | -1.6 % |
| Revs per mile | 562 | 572 | +1.6 % |
| Axle height | 17.94" | 17.64" | -7.5 mm |
| Approved rim width | 6.5–8.5" | 6–8.5" | overlap 6.5–8.5" |
Both are approved on a rim 6.5" to 8.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 235/75R22. Fit 225/75R22 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.2 mph | -0.8 |
| 70 mph | 68.8 mph | -1.2 |
| 90 mph | 88.5 mph | -1.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,835 on the road, so it over-counts by 165. At a true 70 mph the first turns 656 times a minute, the second 667.