The bike swings and ends up in taking up more space. And if there on the wall they don't swing so much when bumped (in my house me, and my parents have like 3 bikes each and hanging, with most touching the wall seem to be the best way to keep them. Just so no one thinks I'm spoiled one of my bikes is a touring bike i bought, one was a free road bike/fixed gear now, and the third is a cross country bike that i just sold to buy my new frame)