T800........
Answers as per your questions:
Option 2 is the nearest fit but let me elaborate, I have the 255/235 option on my car, from new when cold the ESC light flashed when traveling over uneven road surfaces or accelerating a bit harder than normal traffic take up speed.
After fitting MPSS tyres of the same size this condition seemed to worsen, I can say that at the time I was trying different tyres pressure setting to see if running a higher pressure in the rear (3bar rather that 2.7bar) would make a difference, this made it worse so I reset back to OEM spec. Even tyres with the same sizes but from different manufacturers will have a slightly different rolling radius and with the stagger that is already present in the OEM setup (the 255/30 and 235/35 is not the best combo IMHO, 265/30 would have been much better) I concluded that the ESC system calibration was suspect.
As I stated before I was at my dealers for the fuel pressure regulator software update and asked if they would check the logs to see if there was an issue (I did not have a VCDS at the time), I was told by the MT that they had a vehicle that had been shipped with the wrong adaption valve set for the tyre size and that there are 2 values, so he checked mine which was set correctly. The implication of this is if you swap the front from 235 to 255 then the other adaption valve should be used, I have not tried this so I can't comments on what it is like for a 255 vehicle to switch to 235 or vice versa.
It would not be practical for Audi to offer different adaption values for different tyres, only the ones they supply as OEM would be catered for as these would be the ones that testing was carried out with.
With my front tyres considerable more worn that my rears now and running OEM pressures the ESC "issue" is back around the OEM tyre experience of flashing over uneven surfaces (like tram tracks) when anything more that maintenance throttle is open.
hello Arcam,
at home we have 2 RS3, 1 with 255/235 combo and the other one with 235/235.
each one with pirelli tyres.
What I can say is that the one with 255/235 makes the ESC flash easily, with the RS3 and 235/235 combo you have to push harder to see the ESC flashing.
regards