Tires size ?
 

Can i put a 295 40 tire on my 9.5 wide rims overall is 28.3 is this ok for a e53

As long as the rolling diameters for the front and rear are equal (ideal) or <1% difference you should be okay. This is so the 4x4 and DSC stay happy. Just FYI though, the resulting possible bulge may decrease the contact patch (at proper inflation) and may negate the benefits of the wider tires. Will still look cooler though.

I was thinking of doing it in all 4 corners

Should be fine then as long as you have the clearance from the suspension. There are guys here running factory 305's up front so I think you will be fine.

Ok now I just need to find that size at a reasonable price. So just to be clear the diameter just has to match ? If I wanted to can i run a 285 40 ? It's 28" overall just 1" smaller then the factory 29"

That's 285 40 in all 4 corners has well

You can run smaller or larger than factory diameters but it will affect your speedometer accuracy. This is the wheel/tire fitment calculator I use.

https://www.wheel-size.com/calc/

Thank you

295 tire is too wide for 9.5" wheel width.

On a race track, yes I definitely agree with you. On the street, 295's fit just fine on a 9.5" wheel. As I was saying above, there MAY be a slight tire bulge (like this look personally) which would negate some of the increased tire patch. But again, on the street... everything will be fine. I've seen guys run 305's before.