So, how to solve this problem?
Here's a which I recently discovered: use an old bike chain.
Now, your bike chain is the primary means for your bike's locomotion with every turn of your pedals putting energy through your chain and pushing you forward. Even though bike chains are built to be tough, they don't last forever and you can use and old bike chain to protect your seat from thieves.
Here's what you need:
- a bike chain, which you can get at a bike store, if you don't have one laying-around. Mechanics may have a pile of old chains which they can scavenge for parts when they need them;
- a chain tool;
- an old inner tube;
- some electrical tape;
- a zip-tie.
- Using your chain tool, remove one of the pins that holds the chain in its loop;
- loop one end of the chain through the rungs underneath your seat and through the upside down V portion of your frame formed between your seat post and seat stay. How much slack you keep on the chain depends on how often you adjust your seat, if at all. Try to keep it as tight as possible;
- Remove the extra portion of the chain with your chain tool, so your chain is long enough to go from frame to seat and back again in one loop;
- take your old inner tube and measure-out a portion long enough to cover the length of the chain in one loop, with a little extra so the two ends will overlap. Cut off the extra portion.
Put a bit of oil on the chain to protect it against rust.
- Put the chain inside the tube and loop the whole thing between your seat and frame.
- Using your chain tool, reattach the two ends of the chain so it's in one loop again.
- Using your electrical tape, tape the two ends of the tube together, so the chain is completely covered. The oil on the chain will protect it from rusting for awhile, but this isn't a weatherproof seal.
- to keep the chain from moving-around back there, use a zip-tie to secure the two sides together as tightly as possible.