a 245/40 tire on a 17x7 in wheel WILL NOT FIT.
THE TIRE IS TO WIDE AND THE RIM WILL NOT ACCOMODATE IT.
The most you can fit on that rim is 235 ( and I think thats calling it close )
If you want to put 245 width tires you will need to get a 17 x 7.5 or 8 rim.
( doubt will fit on 7.5 )

Theres no easier way to explain this unless I whip out a ruler and physically show you.

dont go by ohh this tire is 20 inches wide so it should fit on this 20 inch rim.

Now the reason you will go down two sizes on the profile is because your trying to fit a wider tire than the rim can sort of handle. So to compensate for the extra width you gotta lower the profile. That way the tire wont buldge out on either size of the rim.

go with 225..and save yourself some headaches.

245 will possibly rubb since your civic's wheel well isnt designed for that.