Sarah:

Just be careful... You bring one bike home, and fall in love with it, and the next thing you know, it gets lonely. So you bring home a companion to keep it company...

Now, you're in for it... It doesn't matter whether you anthromorphosize your bikes as male, female, or maybe one of each. They are bike-sexual, and they'll start to multiply until they fill the space you have to stash them in.

As Zen and others have noted, don't say you weren't warned