245/75R15 vs 225/80R15
Going from one to the other changes the overall height by -1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/75R15 | 225/80R15 | Change |
|---|---|---|---|
| Overall height | 29.5" | 29.2" | -1.0 % |
| Sidewall | 7.23" | 7.09" | -2.0 % |
| Section width | 245 mm | 225 mm | -8.2 % |
| Circumference | 92.6" | 91.7" | -1.0 % |
| Revs per mile | 684 | 691 | +1.0 % |
| Axle height | 14.73" | 14.59" | -3.8 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 245/75R15. Fit 225/80R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,900 on the road, so it over-counts by 100. At a true 70 mph the first turns 798 times a minute, the second 807.
What drivers reported
245/75R15 carries 2 complaints. Nobody has filed one naming 225/80R15.