Cycle Advice - Storing Your Bike
INDOOR STORAGE
The best of all options. If this is possible for you, then try to use this option every time. Controlled climate is the best way to keep your bike healthy over the winter. The best place would be within your house; lockers that are sometimes found in flats are often the favorite shopping place for bike thieves. Garages are vulnerable too; thieves know they can break into a garage often without disturbing the occupants of the main house. If you do use the garage, don't forget to lock the bike to something within the garage. Thieves are usually lazy and also in a hurry, so will always go for what's easy - never for anything even a little difficult.
OUTDOOR STORAGE
The less desirable of both options, but sometimes the unavoidable one. At the very least, your pride and joy should be covered with a tarp of some kind, or left under a roofed structure or in a shed. The enemy here is prolonged exposure to humidity. Strip the bike of all removable and delicate components. Leather seat, bike computer, saddle bags and anything you can easily remove should be stored indoors. You can buy bike covers for about £30-35 which are waterproof and UV resistant.
GENERAL TIPS
Here are some things you should do before leaving your bike alone for a long period of time. Lube the chain and all derailleurs. Shift down all derailleurs to remove tension in the cables - i.e. click the small shift lever so that the chain is on the smallest ring at the front (the left hand one); and the smallest ring at the back (the right hand one). This will effectively put the spring in them at rest, and gives the best chance of the gears being right when you ride it again.
Clean the bike to remove any dirt residue that could turn into rust over the winter. The best thing to use for this would be lemon furniture polish. Pledge does a great job, clean with one rag and then buff with another. The wax left from the cleaning should add some protection to the finish. It smells nice too.
Put some air in those tyres. Rubber inner tubes are porous to some degree and you do lose air pressure over time. A low pressure tyre sitting at the same place for a long time will develop a flat spot. Another way to avoid this is to hang the bike from the ceiling, eliminating any contact on the ground with the tyres.
In bike rental places where we store a lot of bikes, you'll see bikes hung up by the front wheel against a wall or sometimes hung from the saddle itself.
Lastly, lock your bike up. Even if it is stored with you in your house, it can still be vulnerable. If you already have a lock, it won't do you any good if it sits in storage in your saddle bags over the winter. Take the extra 30 seconds to get some peace of mind that you have already paid for.