15" snow tires good idea or not?
 

My 2015 Honda Civic Touring Ed comes with 17" steel wheels and lately been thinking about this winter and the possibility of snow .( Last season we had no snow to speak of in the greater Vancouver area of BC ., this year may be different .. ) so now I am thinking of buying snow tires (4 in total.). then I was thinking about also buying steel rims so my factory 17" mag custom wheels won't be salted and pitted., then I started to wonder :

What could happen if I buy four 15" tires and rims? would that throw my speedometer out of whack? and if so by how much? will my suspension sustain the smaller wheels ..??

good questions -- need some honest answers- please ., I'm sure 17" rims and tires could easily out double my wallet from my planned 15" purchases ..

the suspension would be fine spedo mit be off a little bit but the main concern would be fitmeant of the rim. like would the smaller wheel clear your braking and suspension components ???