Hey guys, im pretty new to modding up anything really... but I've been doing some digging around and havent been able to find a concrete answer:

Will putting 275/19 on a G35x Sedan ('05) hurt it/need any modification? and can i go 275/20 possibly?

also recommended ratios for each would be awesome too!

Thanks

EDIT:
on 19" x 9.5" and 19" x 8.5" rims