The difference in diameter is 5%, but the sidewall height differential is actually closer to 8%. The nominal sidewall heights:

- 225/45 (standard size) = 101 mm
- 245/45 (optional rear size) = 110 mm
- 215/55 = 118 mm

8 mm is about 1/3".

Tread depth of a typical tire is 12/32". So the difference between a new and a worn tire (say mounting a "new" spare for a worn one) is 10/32" (or 8 mm). The DSC system would be expected to deal with this.