I am asking the following because after a couple of days of searching, I have not been able to find an answer so please leave your flame throwers and try to give me an educational answer.

I have a 2007 Z and while I am keeping the original wheels, I would like to mount wider tires, specifically 265/40's and 245/40's. However, I found out that some people do not recommend this tire set up mounted on the factory wheels, specially in the rear.

Given that the width difference between the original and the proposed tires is just 20mm (.78") and the fact that the new tires will be lower in height, could someone please tell me why is this set up not a good idea?

 

it would be fine...just check the tire calculator if you have higher than enthusiast model for rolling diameter and match it.