If a tire recommended size is 245/45/R17 and you would to put on 225/45/17..what could possibly happen? how about 205/50/17? thanks

Both those sizes are smaller in load carrying capacity - VERY BAD THINGS COULD HAPPEN!!

how about if the recommended size is 225/55/17....? thanks

Hey cerivera, talk to Grant@TireRack, he could tell you exactly what would happen, but I agree bad things would happen.