205/65R18 vs 225/55R18
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 | 205/65R18 | 225/55R18 | Change |
|---|---|---|---|
| Overall height | 28.5" | 27.7" | -2.6 % |
| Sidewall | 5.25" | 4.87" | -7.1 % |
| Section width | 205 mm | 225 mm | +9.8 % |
| Circumference | 89.5" | 87.2" | -2.6 % |
| Revs per mile | 708 | 727 | +2.6 % |
| Axle height | 14.25" | 13.87" | -9.5 mm |
| Approved rim width | 5.5–7.5" | 6–8.5" | overlap 6–7.5" |
Both are approved on a rim 6" to 7.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 205/65R18. Fit 225/55R18 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 | 68.2 mph | -1.8 |
| 90 mph | 87.6 mph | -2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,737 on the road, so it over-counts by 263. At a true 70 mph the first turns 826 times a minute, the second 848.
What drivers reported
Nobody has filed a complaint naming 205/65R18. 225/55R18 carries 11.