245/60R18 vs 225/65R18
Going from one to the other changes the overall height by -0.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/60R18 | 225/65R18 | Change |
|---|---|---|---|
| Overall height | 29.6" | 29.5" | -0.2 % |
| Sidewall | 5.79" | 5.76" | -0.5 % |
| Section width | 245 mm | 225 mm | -8.2 % |
| Circumference | 92.9" | 92.7" | -0.2 % |
| Revs per mile | 682 | 683 | +0.2 % |
| Axle height | 14.79" | 14.76" | -0.8 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 245/60R18. Fit 225/65R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.9 mph | -0.1 |
| 50 mph | 49.9 mph | -0.1 |
| 70 mph | 69.9 mph | -0.1 |
| 90 mph | 89.8 mph | -0.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,980 on the road, so it over-counts by 20. At a true 70 mph the first turns 796 times a minute, the second 797.
What drivers reported
245/60R18 carries 14 complaints. Nobody has filed one naming 225/65R18.