215/40 17

I have the opportunity to buy some Goodyear Eagle for a very very very good price but they are 215/40 instead of 215/45... shouldn't make too much of a difference should it?
 
i'd try one first mate if possible,my mate altered his tyre profile by 5 on his skoda VRS and it made the wheels look so small,he took them off and sold them straight away
 
Yup, that is my main worry, it may make the wheels look too small in the arches

hmmm i think they might look to small mate,granted my mates skoda was a bigger car so the wheels may have looked small because of this but we both thought the wheels looked small just in the arches,his VRS also ran 17's,bigger tyres though i must add,think he went from 55's to 50's,it did look really bad mate tbh
 
You will make the ride worse and lose an amount of rim protection. The Speedo will over read.