245/65R15 vs 225/70R15
Going from one to the other changes the overall height by -0.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/65R15 | 225/70R15 | Change |
|---|---|---|---|
| Overall height | 27.5" | 27.4" | -0.5 % |
| Sidewall | 6.27" | 6.20" | -1.1 % |
| Section width | 245 mm | 225 mm | -8.2 % |
| Circumference | 86.5" | 86.1" | -0.5 % |
| Revs per mile | 732 | 736 | +0.5 % |
| Axle height | 13.77" | 13.70" | -1.8 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 225/70R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.8 mph | -0.2 |
| 50 mph | 49.7 mph | -0.3 |
| 70 mph | 69.6 mph | -0.4 |
| 90 mph | 89.5 mph | -0.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,950 on the road, so it over-counts by 50. At a true 70 mph the first turns 854 times a minute, the second 859.
What drivers reported
Nobody has filed a complaint naming 245/65R15. 225/70R15 carries 49.