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bluefoxicy 06-07-11 03:30 PM

I'm thinking of buying one, as I got a cable lock right now and I want a chain, but there is good argument for a good U-lock.

I've seen the Nashbar OnGuard recommended, as well as the Kryptonite New York lock (apparently designed for New York, imagine that), both of which resist ... basically every kind of attack.


NightShift 06-08-11 05:48 AM

Chains, with good locks, MAY be harder for a thief to defeat than a U lock, and they can definitely be used in ways/situations U locks can't.

I use a chain for my Bike E (single beam recumbent), camping, and when I expect to have trouble finding something to lock up to.

U locks are lighter and easier to carry.

I use a U lock for my patrol bike (when possible) and for my beater/grocery getter.

OnGuard makes makes some good U locks and some so-so U locks.

fietsbob 06-08-11 09:24 AM

see the boron carbide steel alloy chain thread,
the steel alloy used is what makes it harder to cut.

bluefoxicy 06-08-11 10:41 AM

That's true, but high carbide steels are good for chains ... if we made a U lock out of boron carbide, it'd crack from a bottle jack easy. Steel with that high carbide content is more brittle than regular steel. Soft mild steel will flex, stretch, and fatigue under stress before breaking.

You need a type of steel that flexes, but that is hard enough to resist flexing. If it's very hard, it'll resist a ton of force; but when you apply it, it'll shatter. If it's soft, you can bend it up until it breaks. If it's hard, but flexible, it'll bend and stretch under excessive force at its weakest points, requiring much more energy to defeat. It might take 0.95 tons instead of 1 ton, but it'll take 0.95 tons applied consistently, enough to force a permanent deformation, and over a longer reach. Further, the metal will be harder to force into fatigue, meaning you might completely mangle the lock without actually breaking it--if the clasp holds.

And, still, it has to resist cutting, sawing, refrigerants, impact, and compression attacks (bolt cutters). I'm not saying you can't take out boron carbide steel with a rotary tool and cutting disc; but you're going to need a stack of cutting discs and about 10-20 minutes depending on steel quality and thickness. Bolt cutters? Literally, you're talking about an explosion here, you're going to need 30,000 pounds of force.

This won't happen with steel useful for U-locks. They might resist bolt cutters, but not quite as well. They'll resist sawing, not quite as well as harder steel, but well enough. Cutting disc? Short work, the metal's going to peel off. Bottle jack? Hammers? Oh yeah, the steel actually flexes instead of shattering, so even if you overcome its strength, you've ... managed to dent it. Slightly. Good job. High-hardness carbide steel will likely just break the hammer, but shatter under bottle jack pressure.

It turns out you need different tools to crack different locks.

chibibike 06-08-11 11:08 AM

no chains are not good unless it's some uncommon metal that can't be cut. A small U lock is the best thing to get.

bluefoxicy 06-08-11 12:25 PM

Originally Posted by chibibike (Post 12757920)
no chains are not good unless it's some uncommon metal that can't be cut.

U-locks are made out of metal too, so if the chain can be cut, so can the U-lock. You can make a chain harder to cut than a U-lock; the typical U-lock attack is a bottle jack, which as I said will crack the metal a high carbide chain is made out of but fail to a softer and more malleable metal. Of course, the softer metal of a U-Lock is more vulnerable to abrasion attacks and thus cutting discs on a power tool, whereas a high carbide steel chain will resist power tools for several minutes.

This issue is more of what U-Lock to get. Kryptonite U-Locks range from "Bust with a bottle jack" to "Busts a bottle jack," or so I'm told. You can shim some types of shackle locks (the spring-loaded ones Master Lock uses are the standard for a lot of padlocks; the Kryptonite high-security U-locks use dead bolts, which I interpret to mean you have to turn the key to lock them, sliding a bolt in place... shim won't work). Cheaper U-locks like you get at Wal-Mart can be cut with a 47 inch bolt cutter, good waste of $20 there.

Then there's locks themselves. Various types of barrel keys have various attacks, from Bic pens to hollowed barrels (the barrel is always hollow, but if you cut slots on the key points and fiddle around with paper clips you can twist the lock while doing regular old lock picking). Combination locks have various flaws from being able to see the pins to jamming at the correct combination under pressure, so you pull the shackle tight and roll the numbers from the last one back and it sticks at the right combination. The primary defense mechanism of dial-type combination locks is the use of false tumblers, which you can detect through various methods, allowing for a vanilla stethoscope attack.

I have lifetime protection against rubber hose lock picking. The rest requires a lock that's simply not vulnerable to those attacks. I don't have a defense against power tools--even high-carbide steel will cut eventually from a rotary cutting disc, despite being difficult to machine.

The $20 mini U-lock from Wal-Mart isn't going to be as secure as a properly made U-Lock that may cost 4 or 5 times as much. Then again, Mark Tobias showed that a $50 Kryptonite U-Lock failed in 3 seconds against a Bic pen; you paid for a name, not a lock.

chibibike 06-08-11 01:01 PM

well the U lock I got was a medium size one and it was so expensive around 55 dollars i think and I have to turn a key to lock it. i dont' remmeber the brand. Yeah those U locks that use those weird round shaped keys arn't good. My lock uses a real werid looking straigt key and it looks like a normal key hole.

Ediblestarfish 06-08-11 04:19 PM

A Kryptonite Evo is good enough for day parking. The NY version is a beefier version of the Evo, but it's incredibly heavy (go to a store and heft one)--I think it's overkill, but if you feel more comfortable with it, go ahead. Neither will help you much overnight where a thief will likely strip your components and leave the locked parts in place.

I've never seen a cable lock work against anything more than the passing opportunist thief with just some tools and hand wire cutters. Meter long cable cutters go right though the expensive armored cable locks in a snip or two.

I guess the best thing to do is park next to a less secure bike that is more tempting to steal.

himespau 06-09-11 12:38 PM

I've wanted a chain lock but the weight (and cost) of good ones always put me off. And yes, I ride a cheap bike so cost is relevant if the lock costs more than the bike did.

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