Does original FK2 fit 18 inch rims on an FK1???

Hello guys, I’m not new here in the forum, but actually drive BMW, but we (parents and I) could not convince my younger brother of the advantages of a BMW ́s. :-)) But fun with side, doesn’t want to piss you off, also buddies drive the Honda. Have the following question and hope you can help me: So he bought himself a Honda Civic FK1 1.4 Sport. Standard are indeed 17 inch Alu ́s. He wants now however now 18 inch rims of the 1.8 sport (see at honda.de under Zu have talked to the dealer about release for the 1.4, which says there is net since the 1.8 other damper would have in it and therefore the 18 inch rims under 1.4 would be sanded when infusing. But that can actually be garnet, because there is also the 17 inch in 7.5 inches wide. In addition, the cross-section on the 18 inch is smaller (from 225/45-17 to 225/40-18 ) so that the roll circumference is correct and the speedometer net has to be adjusted. ??? The carousel is not different from the 1.8. He only has a different engine, or do I have a mistake of thinking somewhere?? Thanks for your help!!! Greeting Christian