225/55R18 vs 215/60R18
Going from one to the other changes the overall height by +1.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/55R18 | 215/60R18 | Change |
|---|---|---|---|
| Overall height | 27.7" | 28.2" | +1.5 % |
| Sidewall | 4.87" | 5.08" | +4.2 % |
| Section width | 225 mm | 215 mm | -4.4 % |
| Circumference | 87.2" | 88.5" | +1.5 % |
| Revs per mile | 727 | 716 | -1.5 % |
| Axle height | 13.87" | 14.08" | +5.3 mm |
| Approved rim width | 6–8.5" | 6–8" | overlap 6–8" |
Both are approved on a rim 6" to 8" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 225/55R18. Fit 215/60R18 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 10,149 on the road, so it under-counts by 149. At a true 70 mph the first turns 848 times a minute, the second 836.
What drivers reported
225/55R18 carries 11 complaints. Nobody has filed one naming 215/60R18.