RockyMounts Tandem Mount R4
The TandemMount R4 is simply the best two-seater bike rack on the market. Take the front wheel off and mount your tandem onto the fork mount from the ground. Once the fork is clamped in, lift the rear wheel onto the tray, and voil á.  You will only have to lift half the bike's weight at one time. The R4 is also telescopic and can adapt to carry a single bike and bikes with up to a 78" wheelbase.