205/60R18 vs 225/55R18
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 | 205/60R18 | 225/55R18 | Change |
|---|---|---|---|
| Overall height | 27.7" | 27.7" | +0.2 % |
| Sidewall | 4.84" | 4.87" | +0.6 % |
| Section width | 205 mm | 225 mm | +9.8 % |
| Circumference | 87.0" | 87.2" | +0.2 % |
| Revs per mile | 728 | 727 | -0.2 % |
| Axle height | 13.84" | 13.87" | +0.8 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 205/60R18. Fit 225/55R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.1 mph | +0.1 |
| 50 mph | 50.1 mph | +0.1 |
| 70 mph | 70.1 mph | +0.1 |
| 90 mph | 90.2 mph | +0.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,021 on the road, so it under-counts by 21. At a true 70 mph the first turns 850 times a minute, the second 848.
What drivers reported
Nobody has filed a complaint naming 205/60R18. 225/55R18 carries 11.