Hi Guys
My question is regarding 2009 Audi A6 3.2L Quattro (it’s 2009 but production of 2008 so it’s the pre-facelift) with factory installed 255/35R19 tires and 8.5jx19 ET48 wheels. The car also has option 1BE which is the sport suspension.

I just bought the car last week and I must change the tires because they are in terrible condition. The original owner said he had difficulty finding this tire size and upon searching at the main traders, I also didn’t find it. I also think the wheels might have some defects because there is vibration and noise above 100 km/h. Roads here also have many pot holes or horizontal lines so the ride isn’t really nice with such a heavy car and low profile tires. I am currently driving an A4 B8 with standard suspension ad 225/55R16 tires and to be honest I don’t feel the “comfort” of the A6 at all !

For that, I will buy new 18” wheels as the 18” tires is commonly available here for BMW and Mercedes Sedans. My current wheel is 4f0601025BA with ET48. I am thinking of buying either 4F0601025CD (which is 8.0j ET48) or 4F0601025AL (which is 8.5j ET46).

If I do, the tire size available widely here is 245x45 R18, because it is used on the 5-series. The car catalog indicates that at 18”, the tire size is 245x40. I made some calculations and came up with the following :-
The outer tire diameter of my 255x35R19 : 661.1mm
The outer tire diameter incase of 245x40R18 : 661.2mm (not available)
The outer tire diameter incase of 245x45R18 : 677.7mm (widely available)

My questions are (I need opinions please because I will be shipping the wheels from the US, and the tyres are expensive so I don't want to make a mistake !) :-
A- Has anyone tried the 245x45R18? Would it fit? Do you have pictures?
B- Is there a concern about rubbing? The addition in diameter is 677.7 – 661.1 = 16.6mm
C- Is there a preference to go for the 8.5j (like original) or is 8j enough? Tires will not exceed 245 wide and I can see 8j can take up to 245.
D- Will I be at risk to damage anything in the suspension by using such a profile (45)?
E- What are the differences between the sport suspension and the standard one? Because I am suspecting the A6 must be much more comfortable than this !!