Trying to figure out what size tires I should roll with. My ride comes with the sports suspension. Going to pick up some 166 oems.

 

tire size different from a 2007 525i vs a m5?

 

If i am lowering the car with H&R Sports springs, does tire size make a difference?

 

Of course. Fatter tire---> rubbing. Unless of course you roll your fenders. Although I think BMW designed their fenders just fine haha.
Also, I'm not saying you'll definitely run but rather it was a response to your "does tire size make a difference".

Take pics!

 

so what would be the ideal size tires to get for 19x9.5 rear and 19x8.5 front with sports suspension and H&R sports springs?

 

I run Hankook Ventus V12 evo K110 tires in the following combo:

front 245/35 R19 on 19x8.5 rims with +15 offset
rear 285/30 R19 on 19x9.5 rims with +22 offset

These slightly larger rear tires have the same outside diameter (circumference) as the front tires (that's good)
and they fill up the wheel well a bit better.

Mine do not rub, BUT my rear fenders have been rolled.

Keep in mind--- most rubbing issues are caused by improper offset of your wheels--- and could rub on the inside of the wheel well, the outside fender, or even the suspension.
With the right offsets you can run 285 width on the back no problem.

 

Avoid a 255 on the front if you don't have M5 fenders...they're more likely to rub. A 245 should fit just perfect.

 

Are you on SF-71s by any chance?

 

sorry not to respond sooner. I found a very unique set of Cross JIC Stella 5 wheels... trying to attach a pic of one of the wheels.
Also tried to attach a pic of a 3 series running the same style of wheels (different offsets, but 19" like mine).
I need to take pics of my 545 and build up my profile, 'cause they look quite good.

They are admittedly a bit old-school, remind me of rims from a Ferrari 360, but I still love 'em.
Probably the only 5 series in North America running these things.