245/65R16 vs 225/75R16
Going from one to the other changes the overall height by +2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/65R16 | 225/75R16 | Change |
|---|---|---|---|
| Overall height | 28.5" | 29.3" | +2.6 % |
| Sidewall | 6.27" | 6.64" | +6.0 % |
| Section width | 245 mm | 225 mm | -8.2 % |
| Circumference | 89.7" | 92.0" | +2.6 % |
| Revs per mile | 707 | 689 | -2.6 % |
| Axle height | 14.27" | 14.64" | +9.5 mm |
| Approved rim width | 7–9" | 6–8.5" | overlap 7–8.5" |
Both are approved on a rim 7" 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 245/65R16. Fit 225/75R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.8 mph | +1.8 |
| 90 mph | 92.4 mph | +2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,262 on the road, so it under-counts by 262. At a true 70 mph the first turns 824 times a minute, the second 803.