Bike Seat Chain Lock (that Doesn't Look Stupid)





Introduction: Bike Seat Chain Lock (that Doesn't Look Stupid)

I've seen lots of bike seat locks made from bike chains that look stupid - they're giant loops of bike chain haphazardly looped around the seat rail and the bike frame that flap in the wind.  Effective, sure, but they look like crap. Who wants that?

My bike seat [bike] chain lock really isn't anything wildly different, but I think it looks quite a bit better by using a little less chain and shrouding the chain in a piece of innertube.

Step 1: Materials, Tools

Clearly the most critical part of the equation is a bike chain:

Go to your local bike shop and nicely ask for an old chain that they've discarded.  The nice bike mechanic should oblige you with some old chain - 2 feet should be more than enough.  If they say you'll have to buy one, I'd go to another shop - bike shops usually have these things in the garbage can so I wouldn't pay for one (although bike mechanics always like tips - throw em a few bucks and the next time you get your bike serviced there, there's a good chance you'll get A+ service).

Greasy chains are good.  Although they're messier to install, the grease ensures that the chain won't rust and deposit rust marks where the chain is looped around your frame.

You'll also need a chain break and around a foot of innertube.  I use some 700c by 18-23.  Certainly you can use any size that you want, but like I said earlier: loose = stupid looking; you don't want anything flapping in the wind.

Step 2: Pin in Last Link of Chain

It'll make your life MUCH easier if the pin is in the last link of the chain, as pictured.

If the bike mechanic gives you some chain and it doesn't look as pictured, don't fret.  Use your chain break and take a link of chain off, but don't push the pin all the way through.

If this doesn't make sense, you've probably never used a chain break; after you use it once, perhaps twice, it'll be pretty obvious.

Step 3: Break the Chain, Cut the Tube

Loop the chain around the rear triangle and your seat rail, figure out the least amount of chain necessary.  A little loose is much easier to install than a little tight, so if the distance is kinda between chain links, leave an extra link in.

You should have one end of the chain that looks like the pic in the previous step (with the pin in it), and the other end should look as pictured here.

At this point, cut some innertube.  This is also ok to leave a few inches long - I cut the innertube where my fingers are, which you can see are a few inches below where the chain wraps around the rear triangle.

Step 4: Connect the Chain

This is where my method differs from the crappy looking ones out there.

Loop the chain over the seat rail, but leave one end hanging a few inches above the rear triangle.  Equivalently, the other end of the chain will be a few inches below the rear triangle.

Then feed the innertube over BOTH ends of the chain, and feed the entirety of the innertube over the chain, so that the tube is bunched up and both ends of the chain are exposed.  Get something thin and insert it through both sides of the chain so that it keeps the innertube from sliding down (you can see in the picture that I used a small drill bit, or an old spoke is a natural chioce).

Then loop the chain around the bike frame and connect the chain.

Step 5: And You're Done

Pull out whatever stop you were using (spoke, drill bit, bobby pin), pull the innertube uniformly over the chain, and you're done.

Note: Over time the chain will probably wear the paint on your bike. For another one of these that I made a while ago, I cut a slit in the tube and somehow looped the tube back into itself, so that the tube was between the chain and the frame.  It was kinda like a Klein Bottle.  It's been a while and I can't remember how to do it, but it's possible.

Now that I think about it, you'd just cut a slit in the tube just above the main cut and pull one end of the chain out, then expose the other end of the chain through the main cut where you cut the tube to length.  Connect the ends of the chain and then feed the tube over the exposed part [that you just connected], and up into the slit. Yeah, it's just like a Klein Bottle (or an approximation of one in 3 - space).

Bingo - the tube runs the entire length of the chain (except where the chain loops over the seat rail), and is in between the chain and the frame of your precious bike.

If there's a groundswell of interest, I could post how to do it in an update.

I made this instructable at TechShop!  Although you can't make proper Klein Bottles there (or any other object that lives in 4-space), you can make pretty much anything else!



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could this instructable be turned into a bike security chain?

turned out pretty good. I recommend leaving a little extra chain. I put some inner tube to protect the paint as well. use about 6-8 inches and slice the long piece of tubing about 3/4 inch on both sides and tuck the other tubing into it. I also used a few zip ties to hold the rubber tubing in place better.


Good idea, thanks for sharing.

Thank you for this!

Though I think the 'Klein Bottle' addition would be very useful too...

When I lived in NYC the first thing you did when you got a nice new bike was burn a hole in the seat with a cigarette in a conspicuous place, to make it worthless to steal. Then you either spraypaint or cover your beautiful frame with tape or inner tube rubber to conceal its value. Then you get rid of all the quick release levers and replace them with bolts. Finally you get a chain that could hold King Kong down. Even so you were best off taking your bike indoors, as even the crappiest looking bike eventually got stolen (as all of mine did).

Interesting idea! You could also slip a couple pieces of tubing (like heat shrink or a straw) over the chain before you rejoined it. Keep them long enough so the ends would be covered by the inner tube. Save your frame and any rattling of metal on metal.

1. There are bike saddles that cost upwards of $100 - e.g. , Brooks, that makes it theft worthy.
2. The thieves easily undo allen bolts and regular bolts holding the saddle to the seat post and the seat post in the frame.
3. The chain ties the saddle to the frame via the rails, making the theft more cumbersome if not impossible.

Would it not be easier and more effective to secure the seat with a good old fashioned Allen bolt rather than I quick release? The chain could easily be snapped with two hands. And before you argue that a theif could easily be carrying an Allen key, well I'd be more worried about the several more expensive items on my bike held on with Allen bolts

The tensile strength of a properly assembled bike chain is probably around 20,000 psi, I'd like to meet the chap who could snap that! Good point though!

It wouldn't be tensile strength that you would worry about, bike chains are made to bend only in one plane, bending one sideways, if there is enough slack, it could be broken easily. If secured with little slack, it would be hard to break.