OP; I use the kits that mount to the ceiling and have ropes and pulleys to pull the bikes up to the ceiling. Work great and if you put the kits up at an angle, you can overlap bikes. When done raising half your bikes, lean the other half against the garage wall or use their kickstands. Either way can place a lot of bikes in a small area. Cost about $14 per bike raised or about half that per bike stored. Use two single kits for tandems unless very lightweight ones. Find them in a 5-pack here or sometimes a bit less on ebay.

http://www.amazon.com/5-Bike-Elevati...ceiling+pulley

/K