For rear if you have 11" wide rims - you can put either 305 or 295.

I am more puzzled what size tires to put on front 8.5" wide rims.
All tuners seem to put there 235mm tires, not 245mm. 245 outer diameter also seems to be a bit larger. Is there any common knowledge in what size is the best for front?

Just looked on tires claculator - standard combination of 235/35 and 295/30 19" tires makes rear 14 mm taller.
245 and 295 reduces that difference to 6mm. 245 and 305 has 12mm difference, 235 and 305 makes it 20mm.

So logically I deduce it seems that only valid combinations of tires are 245 with 305 and 235 with 295 if we want to keep original front/rear height difference. Does it make any sense?

 

I can throw out another view on the all seasons. I've been running the Bridgestone 960 PP all seasons. Really sucked during the summer. But in the winter they've been really fine. Solid handling (more or less) in the cold weather and good in the rain. I don't try to drive it in any real snow. The cold temps are deadly for the RE050A's or the PS2's. The AS's are fine in the cold. I had them already on the rims from the prior owner. I think they are a fine "winter" tire, but not a real snow tire. I solved my problem by buying a set of turbo rims with RE050A's. HUGE difference in handling. I'll definitely be bolting them back on next month.
However, don't read this a recommendation for an A/S tire as an "all year" tire. During the summer, the handling is really crap. You miss out on a ton of potential.

 

I have Bridgestone Potenza RE050A with the size of 295/30ZR19 at the rear.....but they are not available on Tirerack.com. They have 305/30ZR19 as original equipment. What gives?

 

In the selection they have both the 305/30-19 and the 295/30-19 listed. the 295's are at the bottom. If you click on View OE Tires, Size2 box (seems between front and rear), the 295's show @ $325 for the rears. These are the N-1 tires. (the display also shows the fronts @ $255 each.

Enjoy....