not a great deal to be honest, as your going to a wider tyre the profile of the tyre will increase even though its still a 40 as its 40% of the 245 and the others are 40% of 235 , so the 245's will be a slightly taller tyre, not by much though.
I think if you wanted to keep the same rolling specs you would probably have to change to a 245 with a lower side wall ratio to offset the wider tyre....or something to that effect, i expect you will get a full and indepth answer shortly.
rob