# Cheap DIY bike security chain



## coil-n-oil (Jun 22, 2008)

In light of the recent thread on stolen bikes, I figured I'd post this. I also posted it over at PB, so you might have already seen it.

When doing some research on bike security chains, I found a great alternative to the expensive chains that Kryptonite and other companies sell, commonly known as "grade 70 transport chain." This is the gold/yellow colored chain you'll sometimes see at the hardware store, off-road truck stores, etc. both by the foot and in 20ft sections with hooks on the end. The 5/16" variation is common and is listed as having 4700lb load limit. I got a box of 20ft at Harbor Freight for about $30 and made a couple chains. In the perfect conditions of a shop with a concrete floor, it took about 30-60 STRENUOUS seconds of bouncing on the handles and repositioning the link in order to cut the chain with 36" bolt cutters. As long as you don't lock your bike up in such a way that a thief can get the chain/lock on solid ground, he is not going to like this. Even if he did get the chain into a good position, this will not be the quick and easy snatch-and-grab he prefers. If you don't believe me, pick up a test section of this chain and try to cut it yourself. This chain is no joke.

If you want to step it up a notch, you can get the 3/8" version of this chain which should be impervious to any bolt cutters short of the ones that are as tall as a man and as costly as a DH bike (these bolt cutters will also cut any Kryptonite, etc. chain as well). The best price I found on this chain was $70 for 20ft at Tractor Supply, but once again, you can make a few separate security chains from this length. I left the 20ft. section whole so I could lock up 6 DH bikes in the back of my truck when lunch/dinner facilities left the bikes out of sight.

The easiest way to cut this chain for yourself is with an angle grinder, or metal cut-off saw. Pull an old tube over it for protection and secure the ends with duct/gorilla tape and you are good to go. You are going to need a minimum 2.1" tube for the 5/16" chain and 2.3" for the 3/8". Don't skimp on the lock. Almost all the 3/8" locks are weaker than this 5/16" chain. I'd go with a 7/16" shackle minimum and preferably one you could verify as a good performer.

ANY chain/lock can be defeated, so you are trying to minimize your risk and make your bike a harder target than the next guy's. My main concern is the random daylight crime of opportunity with 36" bolt cutters (guy sees your bike, jumps out and snips the chain/cable with bolt cutters and is on his way). The way I see it, this chain (especially the 3/8" version) is close enough in toughness to the expensive security chains, that if you lost a bike while using it, the expensive chain probably wouldn't have helped you. See this video of high-end motorcycle security chains being cut with monster bolt cutters: 




The finished product:


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## DeeEight (Jan 13, 2004)

The only way to cut that chain effectively is with a hydraulic cutting jack. Hardware stores usually have one, bolted to the display rack next to the chain bins. Some are manual handle pumps (like the handle of a car jack) and others are electronically controlled. They both work the same and you get a nice KAPOW when the link snaps. The kryptonite chain IS the transport chain, just in the square link variety. I've got some of the 3/8" stuff, its rated for 7,000 pounds-ish as I recall.

http://www.awdirect.com/bulk-chain/


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## Narco (Jul 7, 2010)

your padlock would be the weak link at this point wouldnt it?


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## 4JawChuck (Dec 1, 2008)

If your looking for a good lock here's the best, solid case hardened steel body and shielded boron alloy steel hasp.

Military grade American lock.










If they are breaking this lock they are serious.


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## Yogii (Jun 5, 2008)

Liquid Nitrogen! Bike is gone...
I prefer 20 grams of C4 in the seat tube with a cell phone ignitor. Lost 3 bikes in the last 8 years. Last one had a lock and chain like you posted. Now my bike stays in my bedroom...


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## DeeEight (Jan 13, 2004)

I know someone who built a shotgun into the seattube of his bike. Basically a spring loaded cylinder sitting under the seatpost. When he locks his bike, he flips open the QR... anyone who sits on the saddle pushes the post down which cocks the spring. When the post lifts up, the safety catch releases. Next depression of the post, BLAM. He usually loads rock salt or solid rubber balls and runs one of those anatomic saddles with the relief cuttouts.

Alternatively you can rig your bike to self-destruct if stolen in a similar way... a hundred grams of thermite packed into the downtube by the BB shell and an electric igniter and POOF... melted out frame tubes.


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## coil-n-oil (Jun 22, 2008)

Yogii said:


> Liquid Nitrogen! Bike is gone...
> I prefer 20 grams of C4 in the seat tube with a cell phone ignitor. Lost 3 bikes in the last 8 years. Last one had a lock and chain like you posted. Now my bike stays in my bedroom...


That sucks. I don't keep mine outside for just that reason, but if I stop to eat on the way back from a ride or have to run into a store for a couple minutes, I use one of those chains mentioned above. I also plan on using a short section in Whistler this year for locking up the bikes when we eat (It's hard to always keep an eye on your bike in the racks there). It's no replacement for good security practices, but does help when you have no choice or just can't keep an eye on your bike every moment.


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## ae111black (Dec 27, 2008)

DeeEight said:


> The only way to cut that chain effectively is with a hydraulic cutting jack. Hardware stores usually have one, bolted to the display rack next to the chain bins. Some are manual handle pumps (like the handle of a car jack) and others are electronically controlled. They both work the same and you get a nice KAPOW when the link snaps. The kryptonite chain IS the transport chain, just in the square link variety. I've got some of the 3/8" stuff, its rated for 7,000 pounds-ish as I recall.
> 
> http://www.awdirect.com/bulk-chain/


HAHA.....I sell the chain in question @ my place of work http://www.truckpartshawaii.com/ and no you cant cut that with a Hyd cutter as I have one and we only use it for small 1/4"- proof chain and it just barely cuts that.... It's mostly for small stuff that you would find @ a hardware store.. 
BTW if you want to get real crazy I sell 1/2"x20' lengths with grab hooks for $130 :thumbsup:


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## Gasp4Air (Jun 5, 2009)

A 25 lb mtn bike will need a 15 lb chain to secure. A 10 lb chain is good enough for a 30lb bike and a 40lb bike doesn't need any chain at all. So you end up riding 40lbs no matter what.


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## rsilvers (Aug 23, 2015)

25 feet of Grade-70 3/8 chain is $52 delivered on Amazon now. I just got some to make a driveway gate from it, and to lock my boats and motorcycle.


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## rsilvers (Aug 23, 2015)

5/16 cuts very easily, by the way. I wouldn't use it on even a cheap bike.


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## rsilvers (Aug 23, 2015)

I made my own hoe-made bike chains from Grade-70 transport chain (the kind that tow-trucks use for strapping down vehicles), and the surprisingly good Stanley padlocks. I tried cutting the chain with a hack-saw, and it took me about nine minutes for one side of a link, and the blade was spent. I then switched to a Sawz-All, and could do a link in about four minutes.

I made the black chain sheathing out of canvas, and sewed them to size. I tried bolt cutters, but it was not happening. I do have Pewag and Abloy on order.


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## DIRTJUNKIE (Oct 18, 2000)

DeeEight said:


> I know someone who built a shotgun into the seattube of his bike. Basically a spring loaded cylinder sitting under the seatpost. When he locks his bike, he flips open the QR... anyone who sits on the saddle pushes the post down which cocks the spring. When the post lifts up, the safety catch releases. Next depression of the post, BLAM. He usually loads rock salt or solid rubber balls and runs one of those anatomic saddles with the relief cuttouts.
> 
> Alternatively you can rig your bike to self-destruct if stolen in a similar way... a hundred grams of thermite packed into the downtube by the BB shell and an electric igniter and POOF... melted out frame tubes.


Sounds good on paper but guess who goes to prison when the bike thief gets injured or killed?


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## Millennial29erGuy (Feb 5, 2017)

DIRTJUNKIE said:


> Sounds good on paper but guess who goes to prison when the bike thief gets injured or killed?


Thats some spike bike **** right there


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## FullBladdy (Aug 26, 2011)

Weak link is that it is attached to the bike rack which can be cut quickly and fairly easily with tools found at home depot. A guy locally had that happen to him in just a minute or two while the rack was backed up to a wall. Came back and no rack, no bikes. 

I do like the effort and it may take away the opportunistic thief but the pro will be ready with the right tools.


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## rsilvers (Aug 23, 2015)

My bike is chained to the car, not the rack.


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