225/75R15 vs 245/65R15
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 | 225/75R15 | 245/65R15 | Change |
|---|---|---|---|
| Overall height | 28.3" | 27.5" | -2.6 % |
| Sidewall | 6.64" | 6.27" | -5.6 % |
| Section width | 225 mm | 245 mm | +8.9 % |
| Circumference | 88.9" | 86.5" | -2.6 % |
| Revs per mile | 713 | 732 | +2.6 % |
| Axle height | 14.14" | 13.77" | -9.5 mm |
| Approved rim width | 6–8.5" | 7–9" | 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 225/75R15. Fit 245/65R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.1 mph | -1.9 |
| 90 mph | 87.6 mph | -2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,736 on the road, so it over-counts by 264. At a true 70 mph the first turns 832 times a minute, the second 854.
What drivers reported
225/75R15 carries 258 complaints. Nobody has filed one naming 245/65R15.