245 really is too wide for a 7" rim. Most 225 tyres including my Goodyear F1's on the Passat are borderline on a 7". So 245 would need at least a 8" as a minimum, prefferably an 9".
Try some Goodyear F1-GSD3, they grip like glue... though they do wear down quite quickly too.
and not the cheapest, but brilliant wet or dry...