235/65R16 vs 225/65R16
Going from one to the other changes the overall height by -1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/65R16 | 225/65R16 | Change |
|---|---|---|---|
| Overall height | 28.0" | 27.5" | -1.8 % |
| Sidewall | 6.01" | 5.76" | -4.3 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 88.1" | 86.4" | -1.8 % |
| Revs per mile | 720 | 733 | +1.8 % |
| Axle height | 14.01" | 13.76" | -6.5 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 235/65R16. Fit 225/65R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.1 mph | -0.9 |
| 70 mph | 68.7 mph | -1.3 |
| 90 mph | 88.4 mph | -1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,817 on the road, so it over-counts by 183. At a true 70 mph the first turns 840 times a minute, the second 855.