I have a 91 camaro and am running 245-50-16zr and it rides hard I was told if i go to 245/45-17 it wold be a lot hader is that true if i go from a 50 to 45 on the side wall

 

A smaller aspect ratio %, combined with going from a 16" to a 17" wheel (what new wheels are you getting?) will give you a shorter sidewall, therefore less "cushion".

But really...The difference is SO minimal, it'll hardly be noticeable, unless your butt-meter is real sensitive.

 

mybe slp zr1 17x8

 

A swap from a 245-50-16 tire to an equivalent 245-45-17 tire will make a minor difference in ride, not much for handling.

A lot of the difference may be the tires, most european brands have very stiff sidewalls that hurt the ride - american and japanese tires (typically) have slightly softer sidewalls. YMMV