I want to hang my bikes in the garage from the rafters. Tri bike, road bike, mtn bike. Will it hurt the rims to hang them on a hook by just the rear wheel?
Perfectly safe to do. Only thing to watch out for is if your rims are non-structural carbon fairings (HED JET, Mavic Cosmic Carbone, etc.), then the weight of the bike may damage the fairing.
Hung all my bikes from the rafters in my tiny house. Something like this is cheap and worked perfectly: http://www.acehardware.com/product/index.jsp?productId=17157736