245/65R15 vs 225/75R15
Going from one to the other changes the overall height by +2.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/65R15 | 225/75R15 | Change |
|---|---|---|---|
| Overall height | 27.5" | 28.3" | +2.7 % |
| Sidewall | 6.27" | 6.64" | +6.0 % |
| Section width | 245 mm | 225 mm | -8.2 % |
| Circumference | 86.5" | 88.9" | +2.7 % |
| Revs per mile | 732 | 713 | -2.7 % |
| Axle height | 13.77" | 14.14" | +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 245/65R15. Fit 225/75R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.4 mph | +1.4 |
| 70 mph | 71.9 mph | +1.9 |
| 90 mph | 92.4 mph | +2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,272 on the road, so it under-counts by 272. At a true 70 mph the first turns 854 times a minute, the second 832.
What drivers reported
Nobody has filed a complaint naming 245/65R15. 225/75R15 carries 258.