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I have the black mounted lock you see below, and would like to buy a U/D lock or folding lock, so the bike can't be moved. I would prefer a 12mm wire where one end goes into the mounted lock, but many videos suggest that they can be cut.

There are lots of videos on YouTube, where they use a grinder to saw over the locks, but I am not so concerned about these types of attacks.

Below have I found an U/D lock, which I have no idea if this particular model is good compared to an Abus or Kryptonite of similar weight, but I like that it also functions as a luggage carrier.

Question

How concerned should I be about the leverage attacks, as this U/D lock is fairly long?

Which strengths and weaknesses does U/D and folding locks have compared to each other?

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There are some good folding locks (Abus Bordo is marked as a silver Sold Secure Lock), but the price doesn't make it seem worth over getting a good U lock. I personally use a Kryptonite Fahgettiboutit Mini, and carrying it isn't really an issue since I just bolt it onto my bike rack (certainly there are lighter options though). If you want to have a way to carry stuff, I recommend attaching a rack to the bike (using the rack eyelets) and using it to carry stuff, such as the lock when the lock is not in use. –  Batman May 8 at 2:42
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Note that the quality of the mount on a D-lock varies widely, even within a brand, and with apparently no relation to price. My kryptonite mounting bracket is utterly rubbish: Unusably stiff and only fits a very limited range of tube sizes my down tube and seat tube are too big for it, and the top tube has cables in the way. It also doens;t clamp very tight to the bike. –  Chris H May 8 at 8:03
    
@ChrisH Which Kryptonite model do you have? –  Jasmine Lognnes May 8 at 11:22
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@JasmineLognnes, it looks like a series 2. They claim the bracket fits up to 80mm tubes so maybe they've updated it, but it's still a plastic strap with a screw fastener. Mine has a really poor ratchet that skips a notch if you do it up too tight, but more importantly the force required to get the lock in/out of the bracket is enough to lift the bike including a full pannier (>20kg). Another issue with this model is that you can't take the key out of the lock with it unlocked, which makes locking and unlocking fiddly in a crowded rack. My wife's masterlock does let you take the key out. –  Chris H May 8 at 12:05
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kryptonitelock.com/Pages/HowtoSecure.aspx and sheldonbrown.com/lock-strategy.html are two good links on how to lock (which is as important as having a good lock). Usually putting the lock in a rack or a bag is easier than using hte mount. –  Batman May 9 at 2:02

2 Answers 2

up vote 3 down vote accepted

I think you need to start from the point where you say that any lock is breakable, if the thief is sufficiently determined. But I do think your insurance arrangements will have a bearing on what lock to buy.

So, rather than asking "what lock should I get to prevent my bike being stolen?", I think it makes more sense to ask "what lock do I need to get so that if my bike gets stolen, the insurance co will cough up?"

So essentially rather than asking your question on here, it might be more useful just to contact your insurance company and ask them for a list of approved locks. You don't say where in the world you live, but in the UK there is a "sold secure" scheme which I think a lot of insurers use, with different levels (bronze, silver, gold) required depending on the value of the bike.

Its also worth noting that the lock on its own is most likely only part of the story - my own policy places restrictions on what I can lock the bike to (must be immovable) and where and for how long I can leave the bike unattended.

On the Sold Secure scheme itself, I've spoken to people who say that it is all a marketing ploy to get you to buy certain locks over others, and their rating of a particular lock has no bearing on how good the lock is. This may or may not be the case, but again I'd stress that its not about preventing the bike from being stolen, its about the insurance company paying out.

I'm making an assumption that your bike is insured. If it isn't, you're really taking a punt when you buy a lock. It might be worth going over to the "Sold Secure" web site (or seeing if there is an equivalent scheme in your country) but as I say it is questionable just how objective these schemes are.

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You don't need an unbreakable lock, just one that's harder to break than the ones around it. –  SQB May 10 at 14:15
    
@SQB I disagree. As I say above, what you need is a lock which will cause the insurance company to pay out. First there is no such thing as an unbreakable lock, second how does the op determine that the lock they choose is more or less breakable than other locks on the market? Easier said than done, your comment is impractical. –  PeteH May 10 at 15:00
    
In the United States, there isn't meaningful bicycle insurance available. Bicycles are covered by renter's/homeowner's insurance, but those policies place no stipulation on the lock used. So, in the United States, having a lock that's a good deterrent matters most— many cyclists use pretty bad locks, so simply having a U-lock (in many cities) or a high-end U-lock (in high-theft cities like NYC/SF) used properly makes all the difference. –  Alan Gerber May 11 at 15:15
    
@AlanGerber that's interesting. So how do you choose a lock? Price? –  PeteH May 11 at 16:41
    
I personally like a thick-shackled mini-U lock as my primary lock: –  Alan Gerber May 12 at 17:55

Haven't checked out the folding variety of locks but am currently using a U lock. Personally, a U lock gives me that assured feel that it'll not take a perp just a couple of seconds to pinch my pride, joy and daily escape from packed trains. My bike is parked at a moderately busy place so it'll not be easy to wrench it on the sly. The lock is a little heavy but I'll take that trade off with huge dollop of positive for whats it keeping safe.

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