235/60R18 vs 225/65R18
Going from one to the other changes the overall height by +1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/60R18 | 225/65R18 | Change |
|---|---|---|---|
| Overall height | 29.1" | 29.5" | +1.4 % |
| Sidewall | 5.55" | 5.76" | +3.7 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 91.4" | 92.7" | +1.4 % |
| Revs per mile | 693 | 683 | -1.4 % |
| Axle height | 14.55" | 14.76" | +5.3 mm |
| Approved rim width | 6.5–8.5" | 6–8.5" | overlap 6.5–8.5" |
Both are approved on a rim 6.5" 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 235/60R18. Fit 225/65R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 71.0 mph | +1.0 |
| 90 mph | 91.3 mph | +1.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,142 on the road, so it under-counts by 142. At a true 70 mph the first turns 809 times a minute, the second 797.
What drivers reported
235/60R18 carries 30 complaints. Nobody has filed one naming 225/65R18.