Bought my Q7 as an ex demo with 17,000 on the clock which had Michelins fitted. Changed the tyres immediately as they were well worn! My local tyre retailer recommended General Grabber UHPs, the tyres are 275/45/20. I noticed tyre wear on the edges of the tyres almost straight away and contacted the Audi dealer where I purchased it. They said there wasn't any known problems but offered a free 4 wheel alignment, they found all 4 wheels to be misaligned. After the problem was sorted I managed to get 30,000 miles out of the General Grabbers and have just had another set fitted. They give excellent grip in wet and icy conditions and are relatively quiet on the road. My colleague who travels with me was so impressed by them that he has just had them fitted on his Range Rover! Unfortunately you cannot get a 21 inch version of this tyre, much to the dismay of another friend who is having big problems with his Q7, he has no grip in the snow with 21 inch Pirellis and is currently having problems with the traction control light flashing when driving in a straight line on a motorway in dry conditions at 80+mph. Moral of the story is fit 20inch General Grabbers, get your alignment checked by Audi free of charge and run the tyres at 44psi all round!