235/55R16 vs 225/55R16
Going from one to the other changes the overall height by -1.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/55R16 | 225/55R16 | Change |
|---|---|---|---|
| Overall height | 26.2" | 25.7" | -1.7 % |
| Sidewall | 5.09" | 4.87" | -4.3 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 82.2" | 80.9" | -1.7 % |
| Revs per mile | 770 | 783 | +1.7 % |
| Axle height | 13.09" | 12.87" | -5.5 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 235/55R16. Fit 225/55R16 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 899 times a minute, the second 914.