I have been told, "no cant do that mate"!!!!!!

[Straycat]

Hello, I have just got hold of a 1998 S8 with 255/45/18's on the back and 245/45/18s on the front. The front's are now on the limit and need changing, I got hold of some nearly new tyres from a mate that does track day racing in a Toyota Soarer after he changed them for track tyres but they are 245 40 18s. I have been told by the tyre fitting place that he would not fit them as my car is 4x4 with traction control as they will nacker the gearbox/transfer box????? is this correct
or will they be OK to use. I also had a word with my local Audi place and they told me to buy 4 new tyres as my car should have 245 45 18s.

Any advise will be greatly excepted.
Thanks
Mick