235/70R16 vs 225/75R16
Going from one to the other changes the overall height by +1.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/70R16 | 225/75R16 | Change |
|---|---|---|---|
| Overall height | 29.0" | 29.3" | +1.2 % |
| Sidewall | 6.48" | 6.64" | +2.6 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 91.0" | 92.0" | +1.2 % |
| Revs per mile | 697 | 689 | -1.2 % |
| Axle height | 14.48" | 14.64" | +4.3 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 235/70R16. Fit 225/75R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.0 mph | +1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,116 on the road, so it under-counts by 116. At a true 70 mph the first turns 813 times a minute, the second 803.