[QUOTE] Fenders help to a certain extent, but as vrkelley suggests spray from passing vehicles is a problem.
I seem to remember from cycling days in the past, when all weather roadies would be seen attired in a large Poncho type waterproof covering not only themselves but a large part of their cycles this would seem to have been an ideal solution for some reason no longer in fashion. Maybe a cover like this would be worth a revival

The problem is that most of the "wet" comes from the road.