tire size HELP!

[GilAnthonyy]

new to this site, just bought an 08 mazda6 i touring and i got this guy willing to sell me 245/40-18's for the front and 275/40-18's for the back.. now i dont know about all this tire stuff.. will this work or are these too big?
let me know.
thanks!

 

[_MSprotegy]

way too big for your car. what are the specs on the wheels?

 

[GilAnthonyy]

my wheels right now are 215/50-17 idk what specs are? haha

 

[_MSprotegy]

size, width, offset...