i had a Continental Speed Ride on the rear and a Clement X'plore MSO on the front. running about 60 psi. (both 40+mm tires)

you may think i should have picked a better tire for the rear because of the mud but...there was only a few spots where the mud was REALLY bad. i was able to roll through most of the bad stuff pretty easily with this set up. and when we hit pavement, it road smooth and fast too.