OK, according to the Bridgestone website, outside diameters are as follows:
- 050a at 215/45R18:- 652mm
- 050a at 215/45R17:- 626mm
- 050a at 225/40R18:- 637mm
- 050a at 225/45R18:- 659mm
- Adrenalin at 225/40R18:- 637mm
- Adrenalin at 225/45R18:- 660mm
RE050a page
Adrenalin RE001 Page
So, if your original tyre was a 215/45R18 (sorry, I can't work out what people are comparing to in the last few posts) the 225/40 will indicate faster than the 215/45 while the 225/45 will indicate slower (producing a greater risk to your licence as you are more likely to be travelling faster than your speedo indicates).
The 225/45 will be closer than the 40 aspect tyre to the 215/45 (4% vs 7%) It won't be exact though (unless you are stretching it across an 8.5" wide rim

)