235/75R17 vs 225/75R17
Going from one to the other changes the overall height by -1.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/75R17 | 225/75R17 | Change |
|---|---|---|---|
| Overall height | 30.9" | 30.3" | -1.9 % |
| Sidewall | 6.94" | 6.64" | -4.3 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 97.0" | 95.2" | -1.9 % |
| Revs per mile | 653 | 666 | +1.9 % |
| Axle height | 15.44" | 15.14" | -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 235/75R17. Fit 225/75R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.4 mph | -0.6 |
| 50 mph | 49.0 mph | -1.0 |
| 70 mph | 68.7 mph | -1.3 |
| 90 mph | 88.3 mph | -1.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,809 on the road, so it over-counts by 191. At a true 70 mph the first turns 762 times a minute, the second 777.