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This doesn't appear to be a dupe of any of the stuck lock issues -- I've only been using the lock for 3 days and the key turns fine. It's an Abus Ultra 410 which locks at both ends and only one end unlocks. I suspect there's a spring or something failing to return the bolt to the unlocked position at the other end. Unfortunately this is the bottom end of a D-lock that's locked round both chainstays and a rather solid post, so gravity is against me.

The shop where I bought it are trying to help, but I'm looking for ideas as well. There's no room for a bottle jack (deliberately, and not that I have one), and I don't have a cordless angle grinder available. I do have the key (both of them in fact).

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    You should also write to Abus right away.
    – John Zwinck
    Sep 23, 2015 at 12:16
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    I'd first try a few solid hits with something resembling a hammer -- not to attempt to break the lock, but to shake loose anything inside that's stuck.
    – Daniel R Hicks
    Sep 23, 2015 at 12:28
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    @DanielRHicks, that's a good plan. I tried thumping it by hand (in the right place according to the manufacturer) but didn't get anywhere. Unfortunately only this morning I transferred my heavy multitool into the frame bag on my other bike so didn't have anything heavy. You say "not to attempt to break [it]" but I do have access to liquid nitrogen which makes steel brittle (popsci used canned air to freeze a D-lock).
    – Chris H
    Sep 23, 2015 at 12:42
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    You can cut most locks with a Dremel and a cutting disk, which is cheaper and it's something you might have access to but not considered. I used one for this when a D lock jammed on me.
    – Móż
    Dec 9, 2015 at 22:54
  • @Mσᶎ I have a pseudoDremel and decent cutting wheels, but having used it to cut down tools in the past I reckon it would have taken a long time and quite a few wheels. The lock was designed such that a single cut through the D part wouldn't be much help (unlike the kryptonite that would unhook). The big advantage of a Dremel is that it would be possible to battery power of even if it's a mains model with an adaptor. Mine is 12V and so could be run off a car battery.
    – Chris H
    Dec 10, 2015 at 6:50

3 Answers 3

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  1. Have you tried a well-aimed hammer blow while the key is turned in an attempt to use inertial force (instead of spring force) to move the latch piece? Start with taps at first.

  2. Have you tried some lubricant injected into the latch hole, in combination with #1?

If both fail, then you have to go with brute force. An angle grinder is the easiest way to get a D lock off, especially a well-built one like the Abus which uses hardened steel. Fortunately, one leg is free so you only need to cut the other leg off (otherwise, you'd have to make two cuts):

  1. Is there a power outlet located within extension cord range?
  2. Is it close enough that you could get a motor vehicle nearby and use an AC inverter to power a regular grinder?
  3. Have you seen if your local police force or city/university grounds crew can remove the lock for you? They often have to tools for when they need to impound illegally parked bikes.
  4. Tool rental shop
  5. Locksmith (note that they might charge through the nose for a site visit)
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  • 1
    You can get carbide grit hacksaw blades. It will take a little time and elbow grease, but it should do the job. Probably one of the cheaper options if you don't already have a tool to do the job. One review said it took an hour for a 12 mm u-lock. They also have similar blades for jigsaws and reciprocating saws if you have access to that.
    – Kibbee
    Sep 23, 2015 at 12:37
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    @Kibbee, that's interesting and not just for this. If I end up with a dead lock (and they'll probably want it back) I might try a few cutting tools against it at home.
    – Chris H
    Sep 23, 2015 at 12:44
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    Abus have told us where to hit it so your first suggestion looks good. As for power, it's within range but I wouldn't be allowed to use it (the bike is outside a station). That does howver increase the likelihood of there being tools and someone to use them on site.
    – Chris H
    Sep 23, 2015 at 12:45
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    @Kibbee - One problem with using a handsaw is that you run considerable risk of damaging the bike while using it. Just the repetitive motion is apt to scratch the bike finish, plus, in an hour's sawing, you're apt to get tired and cause the saw to bump the bike.
    – Daniel R Hicks
    Sep 23, 2015 at 12:46
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    @ChrisH in the UK it is even clearer that the supplier is responsible, its directly in our consumer protection law without needing to sue. So they were probably being helpful because they had to, rather than simply the goodness of their heart. :)
    – JamesRyan
    Sep 25, 2015 at 9:21
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It turns out that one of the bolts doesn't retract with the locking mechanism (the lock is bolted at each end rather than a hooked end and a single bolt). Here's a full writeup in case it helps anyone with similar difficulties (I couldn't find much online).

With gravity to help, the lock works OK,* but with the dodgy end at the bottom it doesn't unlock. This probably explains why I had no trouble before, but this time the bad end was lower than the good end (though almost horizontal). I couldn't lift the tail of the bike on the rack because there was too much (including another bike) in the way.

In the following pictures the red tape marks the bad end. Locked then unlocked with the bad end at the top -- all OK:

Red (bad) end at top

Locked then unlocked with the bad end at the bottom -- bolt still visible:

Red (bad) end at bottom

According to the manufacturer tapping the end nearest the faulty bolt should free it up. Actually it's not enough just to tap the end (I used a large adjustable spanner), you have to jiggle the key (in and out of the unlocked position) while tapping away at it. That was less tricky on the bike than testing for this post (but scuffing the paintwork isn't a worry on this bike). Pressing the bolt with a finger and no shackle makes this obvious -- you can't push the pin in with the key fully in the unlocked position, only in a position where it doesn't stay by itself (almost fully unlocked).

I also managed (off the bike, and only the first time) the get a shim into the relevant hole with the lock unlocked and jiggle everything to free it up. There's not much clearance to do this, the drinks can shim had to be bent just right.

*It got worse while I tested it to write this post.

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    That is a lousy design for a lock. I assume you'll give it bad reviews on consumer sites.
    – Daniel R Hicks
    Sep 25, 2015 at 11:51
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    @DanielRHicks, I might (though I don't tend to review things), it's clearly a manufacturing defect of some sort. It's on its way back to the manufacturer and I've got a kryptonite to replace it. The idea of the double bolt is to make a single cut through the shackle insufficient to open the lock, unlike the (similarly-priced) kryptonite series 2 which uses a hook at one end.
    – Chris H
    Sep 25, 2015 at 11:55
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    @DanielRHicks: Actually, Abus generally has a very good reputation, their (high-end) locks are among the most resilient in the market. I have used them for years without problems. But maybe there was a manufacturing mishap, or QA was neglected...
    – sleske
    Dec 10, 2015 at 9:49
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    @sleske, Yes, the design seemed solid, but I reckon a spring was fitted wrong/damaged or something along those lines.
    – Chris H
    Dec 10, 2015 at 10:11
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    Had the same issue with an Abus 420 today, this answer saved me. Thanks!
    – Martynnw
    Mar 30, 2018 at 16:43
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Just to confirm, I had the same problem with the Abus 410 this morning. Tapping fairly hard on the end of the lock with a hammer where the bolt wasn't retracting whilst my other half wiggled the key in the lock sorted the problem in a few seconds. Much easier with two people than trying to wiggle and hit the lock at the same time.

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  • Handy information - thank you. Please have a browse of the tour if you're new to SE, and welcome!
    – Criggie ♦
    Apr 1, 2017 at 20:48

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