Safest way to store bike outside (city)
Not answering your actual question, but this might be useful to you.

To get a bike through narrow or awkward spaces, hold the handlebars and pull it up onto its rear wheel so it is pointing straight up. It relatively easy to balance a bike like this and push it around on its rear wheel while holding the handlebars. In this orientation it's about as wide as a person and can be turned in place. It's easy to go down stairs and it's even possible to go up stairs by walking backwards with it. The rear brake can be used to stop it slipping backwards.

If you use this technique you may find you are able to more easily get the bike into your apartment, which will be much preferable to locking it up on the street, with respect to both theft or vandalism and the effects of weather.